The 2009–10 Boston Celtics season was the 64th season of the franchise in the National Basketball Association (NBA). The Celtics finished with a record of 50–32, a 12 win drop off from the previous season. They finished 1st in the Atlantic Division and 4th in the Eastern Conference.

In the playoffs, the Celtics defeated the Miami Heat in five games in the First Round, then defeated the top-seeded Cleveland Cavaliers (in a rematch of the 2008 Conference semifinals) again in six games in the Semifinals, and finally, defeated the second-seeded Orlando Magic (the runner-up of last year's Finals as well as the team that defeated the Celtics in last season's Conference semifinals in seven games) in six games in the conference finals to advance to the NBA Finals for the twenty-first time in franchise history.

The Celtics made it back to the NBA Finals after a one-year hiatus and played against the defending NBA champion and their rival, the Los Angeles Lakers for the 12th time. In a rematch of the 2008 NBA Finals, in which the Celtics defeated the Lakers in six games to capture their seventeenth championship, the Celtics were defeated this time by the Lakers in seven games.

The Celtics would not reach the Finals again until 2022 where they faced Golden State Warriors in a rematch of the 1964 NBA Finals and lost in six games.

Key dates June 25 – The 2009 NBA draft took place in New York City. July 8 – The free agency period started. October 27 – The regular season started with a 95–89 win over the Cleveland Cavaliers. March 24 – The Celtics clinched a spot in the Playoffs with a 113–99 win over the Denver Nuggets. March 26 – The Celtics clinched the Atlantic Division title with a 94–86 win over the Sacramento Kings. April 17 – The Celtics won Game 1 in their first-round playoff series against the Miami Heat (85–76). April 27 – The Celtics won their series against the Miami Heat 4–1 and advanced to the Eastern Conference semi-finals after a 96–86 win in Game 5. May 13 – The Celtics advanced to the Eastern Conference finals after they won their series 4–2 against the Cleveland Cavaliers following a 94–85 win in Game 6. May 28 – The Celtics advanced to the NBA Finals after they defeated the Orlando Magic 96–84 in Game 6 to win the series 4–2. June 17 – The Celtics lost to the Los Angeles Lakers 83–79 in Game 7 of the NBA Finals and failed to capture their 18th NBA Championship.

Summary

NBA Draft 2009

Draft picks

Round Pick Player Position Nationality College/Team 2 58 Lester Hudson PG Tennessee-Martin

Roster

Preseason

|- style="background:#fcc" | 1 | October 7 | @ Houston

| State Farm Arena6,300 | 0–1 |- style="background:#cfc" | 2 | October 9 | New York

| TD Garden18,624 | 1–1 |- style="background:#cfc" | 3 | October 11 | New Jersey

| TD Garden18,624 | 2–1 |- style="background:#cfc" | 4 | October 13 | @ New Jersey

| Prudential Center12,790 | 3–1 |- style="background:#cfc" | 5 | October 14 | Toronto

| XL Center10,117 | 4–1 |- style="background:#cfc" | 6 | October 18 | @ Toronto

| Air Canada Centre13,607 | 5–1 |- style="background:#fcc" | 7 | October 20 | @ New York

| Madison Square Garden18,792 | 5–2 |- style="background:#cfc" | 8 | October 21 | @ Cleveland

| Value City Arena18,021 | 6–2

Regular season

Standings

Game log

|- bgcolor="#bbffbb" | 1 | October 27 | @ Cleveland | | Paul Pierce (23) | Paul Pierce (11) | Rajon Rondo (10) | Quicken Loans Arena20,562 | 1–0 |- bgcolor="#bbffbb" | 2 | October 28 | New Orleans | | Ray Allen (18) | Shelden Williams (9) | Rajon Rondo (11) | TD Garden18,624 | 2–0 |- bgcolor="#bbffbb" | 3 | October 30 | Chicago | | Paul Pierce (22) | Shelden Williams (10) | Rajon Rondo (16) | TD Garden18,624 | 3–0

|- bgcolor="#bbffbb" | 4 | November 1 | New Orleans | | Paul Pierce (27) | Kevin Garnett, Kendrick Perkins (7) | Rajon Rondo (10) | TD Garden 18,624 | 4–0 |- bgcolor="#bbffbb" | 5 | November 3 | @ Philadelphia | | Paul Pierce (21) | Paul Pierce (8) | Rajon Rondo (5) | Wachovia Center 11,251 | 5–0 |- bgcolor="#bbffbb" | 6 | November 4 | @ Minnesota | | Rajon Rondo (18) | Kevin Garnett (11) | Rajon Rondo (6) | Target Center 19,133 | 6–0 |- bgcolor="#ffcccc" | 7 | November 6 | Phoenix | | Kevin Garnett (26) | Kevin Garnett (8) | Rajon Rondo (11) | TD Garden 18,624 | 6–1 |- bgcolor="#bbffbb" | 8 | November 7 | @ New Jersey | | Paul Pierce, Rajon Rondo (16) | Kevin Garnett (13) | Paul Pierce (7) | Izod Center 16,119 | 7–1 |- bgcolor="#bbffbb" | 9 | November 11 | Utah | | Kevin Garnett (18) | Kendrick Perkins (8) | Rajon Rondo (11) | TD Garden 18,624 | 8–1 |- bgcolor="#ffcccc" | 10 | November 13 | Atlanta | | Paul Pierce (24) | Kendrick Perkins (9) | Rajon Rondo (9) | TD Garden18,624 | 8–2 |- bgcolor="#ffcccc" | 11 | November 14 | @ Indiana | | Ray Allen (24) | Kendrick Perkins (13) | Paul Pierce, Rajon Rondo, Ray Allen (4) | Conseco Fieldhouse18,165 | 8–3 |- bgcolor="#bbffbb" | 12 | November 18 | Golden State | | Paul Pierce (19) | Kendrick Perkins, Rajon Rondo (7) | Rajon Rondo (12) | TD Garden18,624 | 9–3 |- bgcolor="#ffcccc" | 13 | November 20 | Orlando | | Paul Pierce (21) | Rasheed Wallace (13) | Ray Allen, Rajon Rondo (6) | TD Garden18,624 | 9–4 |- bgcolor="#bbffbb" | 14 | November 22 | @ New York | | Paul Pierce (33) | Kendrick Perkins (13) | Rajon Rondo (10) | Madison Square Garden19,763 | 10–4 |- bgcolor="#bbffbb" | 15 | November 25 | Philadelphia | | Paul Pierce (27) | Kendrick Perkins (8) | Rajon Rondo (7) | TD Garden18,624 | 11–4 |- bgcolor="#bbffbb" | 16 | November 27 | Toronto | | Ray Allen (20) | Kevin Garnett (7) | Rajon Rondo (11) | TD Garden18,624 | 12–4 |- bgcolor="#bbffbb" | 17 | November 29 | @ Miami | | Kevin Garnett (24) | Kendrick Perkins (13) | Rajon Rondo (11) | American Airlines Arena18,104 | 13–4

|- bgcolor="#bbffbb" | 18 | December 1 | @ New Orleans | | Ray Allen (27) | Kendrick Perkins (12) | Rajon Rondo (9) | Time Warner Cable Arena15,129 | 14–4 |- bgcolor="#bbffbb" | 19 | December 3 | @ San Antonio | | Kevin Garnett (20) | Kevin Garnett, Kendrick Perkins (7) | Rajon Rondo (12) | AT&T Center18,581 | 15–4 |- bgcolor="#bbffbb" | 20 | December 4 | @ Oklahoma City | | Kevin Garnett (23) | Kevin Garnett, Kendrick Perkins (8) | Rajon Rondo (6) | Ford Center18,203 | 16–4 |- bgcolor="#bbffbb" | 21 | December 8 | Milwaukee | | Kevin Garnett (25) | Kevin Garnett, Rajon Rondo (9) | Rajon Rondo (13) | TD Garden18,624 | 17–4 |- bgcolor="#bbffbb" | 22 | December 10 | @ Washington | | Rajon Rondo (21) | Kendrick Perkins (11) | Rajon Rondo (11) | Verizon Center20,173 | 18–4 |- bgcolor="#bbffbb" | 23 | December 12 | @ Chicago | | Rajon Rondo (16) | Kevin Garnett (10) | Rajon Rondo (14) | United Center21,257 | 19–4 |- bgcolor="#bbffbb" | 24 | December 14 | @ Memphis | | Paul Pierce (19) | Kevin Garnett (8) | Rajon Rondo (9) | FedExForum14,193 | 20–4 |- bgcolor="#ffcccc" | 25 | December 18 | Philadelphia | | Kevin Garnett (21) | Kendrick Perkins (16) | Rajon Rondo (10) | TD Garden 18,624 | 20–5 |- bgcolor="#bbffbb" | 26 | December 20 | Minnesota | | Paul Pierce (29) | Kendrick Perkins (11) | Rajon Rondo (15) | TD Garden 18624 | 21–5 |- bgcolor="#bbffbb" | 27 | December 22 | Indiana | | Ray Allen (23) | Rasheed Wallace (13) | Rajon Rondo (9) | TD Garden18,624 | 22–5 |- bgcolor="#bbffbb" | 28 | December 25 | @ Orlando | | Ray Allen (18) | Rajon Rondo (13) | Rajon Rondo (8) | Amway Arena17,461 | 23–5 |- bgcolor="#ffcccc" | 29 | December 27 | @ L.A. Clippers | | Rajon Rondo (20) | Tony Allen (10) | Rajon Rondo (6) | Staples Center19,060 | 23–6 |- bgcolor="#ffcccc" | 30 | December 28 | @ Golden State | | Rajon Rondo (30) | Kendrick Perkins (14) | Rajon Rondo (15) | Oracle Arena19,259 | 23–7 |- bgcolor="#ffcccc" | 31 | December 30 | @ Phoenix | | Eddie House (19) | Kendrick Perkins, Tony Allen (7) | Rajon Rondo (8) | US Airways Arena18,422 | 23–8

|- bgcolor="#bbffbb" | 32 | January 2 | Toronto | | Ray Allen (23) | Kendrick Perkins (10) | Tony Allen (7) | TD Garden18,624 | 24–8 |- bgcolor="#bbffbb" | 33 | January 6 | @ Miami | | Rajon Rondo (25) | Kendrick Perkins (10) | Rajon Rondo (8) | American Airlines Arena19,600 | 25–8 |- bgcolor="#ffcccc" | 34 | January 8 | @ Atlanta | | Paul Pierce (21) | Kendrick Perkins (14) | Rajon Rondo (10) | Philips Arena15,149 | 25–9 |- bgcolor="#bbffbb" | 35 | January 10 | @ Toronto | | Rasheed Wallace (29) | Rajon Rondo (10) | Rajon Rondo (13) | Air Canada Centre19,800 | 26–9 |- bgcolor="#ffcccc" | 36 | January 11 | Atlanta | | Rajon Rondo (26) | Kendrick Perkins (9) | Rajon Rondo (7) | TD Garden18,624 | 26–10 |- bgcolor="#bbffbb" | 37 | January 13 | @ New Jersey | | Paul Pierce (24) | Kendrick Perkins (8) | Rajon Rondo (14) | Izod Center14,112 | 27–10 |- bgcolor="#ffcccc" | 38 | January 14 | Chicago | | Paul Pierce (20) | Kendrick Perkins (10) | Rajon Rondo (7) | TD Garden18,624 | 27–11 |- bgcolor="#ffcccc" | 39 | January 18 | Dallas | | Paul Pierce (24) | Kendrick Perkins (12) | Rajon Rondo (12) | TD Garden18,624 | 27–12 |- bgcolor="#ffcccc" | 40 | January 20 | @ Detroit | | Paul Pierce, Rajon Rondo (21) | Rajon Rondo (8) | Rajon Rondo (7) | The Palace of Auburn Hills17,375 | 27–13 |- bgcolor="#bbffbb" | 41 | January 22 | Portland | | Paul Pierce (24) | Kendrick Perkins (11) | Rajon Rondo (9) | TD Garden18,624 | 28–13 |- bgcolor="#bbffbb" | 42 | January 25 | L.A. Clippers | | Paul Pierce (22) | Kendrick Perkins (15) | Rajon Rondo (12) | TD Garden18,624 | 29–13 |- bgcolor="#ffcccc" | 43 | January 28 | @ Orlando | | Ray Allen (20) | Kevin Garnett, Rajon Rondo (7) | Rajon Rondo (8) | Amway Arena17,461 | 29–14 |- bgcolor="#ffcccc" | 44 | January 29 | @ Atlanta | | Paul Pierce (35) | Kendrick Perkins (12) | Rajon Rondo (8) | Philips Arena18,732 | 29–15 |- bgcolor="#ffcccc" | 45 | January 31 | L.A. Lakers | | Rajon Rondo (21) | Kendrick Perkins (10) | Rajon Rondo (12) | TD Garden18,624 | 29–16

|- bgcolor="#bbffbb" | 46 | February 1 | @ Washington | | Kevin Garnett (19) | Paul Pierce (8) | Rajon Rondo (12) | Verizon Center20,173 | 30–16 |- bgcolor="#bbffbb" | 47 | February 3 | Miami | | Ray Allen (23) | Ray Allen (7) | Rajon Rondo (14) | TD Garden18,624 | 31–16 |- bgcolor="#bbffbb" | 48 | February 5 | New Jersey | | Ray Allen (26) | Ray Allen, Kevin Garnett (7) | Rajon Rondo (11) | TD Garden18,624 | 32–16 |- bgcolor="#ffcccc" | 49 | February 7 | Orlando | | Rajon Rondo (17) | Kevin Garnett (9) | Rajon Rondo (9) | TD Garden18,624 | 32–17 |- bgcolor="#ffcccc" | 50 | February 10 | @ New Orleans | | Paul Pierce (15) | Kevin Garnett, Kendrick Perkins (7) | Paul Pierce, Rajon Rondo (4) | New Orleans Arena14,848 | 32–18 |- align="center" | colspan="9" style="background:#bbcaff;" | All-Star Break |- bgcolor="#bbffbb" | 51 | February 16 | @ Sacramento | | Paul Pierce, Rasheed Wallace (17) | Kevin Garnett (9) | Rajon Rondo (6) | ARCO Arena14,439 | 33–18 |- bgcolor="#bbffbb" | 52 | February 18 | @ L.A. Lakers | | Ray Allen (24) | Kendrick Perkins (14) | Rajon Rondo (11) | Staples Center18,997 | 34–18 |- bgcolor="#bbffbb" | 53 | February 19 | @ Portland | | Ray Allen (21) | Kendrick Perkins (9) | Rajon Rondo (11) | Rose Garden20,618 | 35–18 |- bgcolor="#ffcccc" | 54 | February 21 | @ Denver | | Ray Allen (25) | Glen Davis (7) | Rajon Rondo (11) | Pepsi Center19,818 | 35–19 |- bgcolor="#bbffbb" | 55 | February 23 | New York | | Ray Allen (24) | Kevin Garnett (8) | Rajon Rondo (16) | TD Garden18,624 | 36–19 |- bgcolor="#ffcccc" | 56 | February 25 | Cleveland | | Ray Allen (21) | Kevin Garnett (10) | Rajon Rondo (11) | TD Garden18,624 | 36–20 |- bgcolor="#ffcccc" | 57 | February 27 | New Jersey | | Kevin Garnett (26) | Kevin Garnett (9) | Rajon Rondo (17) | TD Garden18,624 | 36–21

|- bgcolor="#bbffbb" | 58 | March 2 | @ Detroit | | Ray Allen (18) | Kevin Garnett (9) | Rajon Rondo (11) | The Palace of Auburn Hills17,956 | 37–21 |- bgcolor="#bbffbb" | 59 | March 3 | New Orleans |