The Cleveland Cavaliers first began play in the NBA in 1970 as an expansion team under the ownership of Nick Mileti. Jerry Tomko, the father of future Major League Baseball pitcher Brett Tomko, submitted the winning entry to name the team the "Cavaliers" through a competition sponsored by The Plain Dealer; supporters preferred it to "Jays", "Foresters" and "Presidents". Playing their home games at Cleveland Arena under the direction of head coach Bill Fitch, they compiled a league-worst 15–67 record in their inaugural season. The team hoped to build around the number one 1971 draft pick Austin Carr, who had set numerous scoring records at Notre Dame, but Carr severely injured his leg shortly into his pro career and never was able to realize his potential.

1970–1980: The Austin Carr era

The following seasons saw the Cavaliers gradually improve their on-court performance, thanks to season-by-season additions of talented players such as Bobby "Bingo" Smith, Jim Chones, Jim Cleamons and Dick Snyder. The Cavaliers improved to in their sophomore season, followed by a record in 1972–73, and in 1973–74.

In 1974, the Cavaliers moved into the brand-new Richfield Coliseum, located in rural Richfield, Ohio – south of downtown Cleveland in Summit County (now part of the Cuyahoga Valley National Park). The move was done as the Cleveland Arena had fallen into disrepair, and the location was chosen in an effort to draw fans in from nearby Akron and other areas of Northeast Ohio. That season, the Cavaliers finished with a 40–42 record, falling just short of a playoff berth.

"Miracle of Richfield" In the 1975–76 season with Carr, Smith, Chones, Snyder, and newly acquired Nate Thurmond, Fitch led the Cavaliers to a 49–33 record and a division title. Fitch received the league's Coach of the Year award as the Cavaliers got their first winning season, made their first-ever playoff appearance, and clinched their first Central Division Title.

In the playoffs, the Cavaliers won their series against the Washington Bullets, 4–3. Because of the many heroics and last-second shots, the series became known locally as the "Miracle of Richfield." They won Game 7, 87–85, on a shot by Snyder with four seconds to go. But the team became hampered by injuries—particularly to Jim Chones, who suffered a broken ankle.

The Cavaliers proceeded to lose to the Boston Celtics in the Eastern Conference Finals. It is widely believed among both Cavaliers fans and players that the "Miracle" team would have won the 1976 NBA Championship had Chones stayed healthy.

Cleveland won 43 games in both of the 1976–77 and 1977–78 seasons, but both seasons resulted in early playoff exits. After a 30–52 season in 1978–79, Fitch resigned as head coach to take the same position with the Celtics, where he coached the Larry Bird-led squad to the NBA championship in 1981.

1980–1983: Ownership under Ted Stepien The following season, after going 37–45 under Fitch's successor Stan Albeck, original owner Mileti sold his shares to Louis Mitchell who sold the shares to minority owner Joe Zingale. In 1980, after just a few months, Zingale sold the team to Nationwide Advertising magnate Ted Stepien on April 12, 1980. Early on in his tenure, Stepien proposed to rename the team the "Ohio Cavaliers", part of a plan that included playing their home games not just in the Cleveland area but in Cincinnati and in non-Ohio markets such as Buffalo and Pittsburgh. He also made changes to the game day entertainment, such as introducing a polka-flavored fight song and a dance team known as "The Teddy Bears". Stepien also oversaw the hiring and firing of a succession of coaches and was involved in making a number of poor trade and free agent signing decisions. The result of his questionable trading acumen was the loss of several of the team's first-round draft picks, which led to a rule change in the NBA prohibiting teams from trading away first-round draft picks in consecutive years. This rule is known as the "Ted Stepien Rule".

The ensuing chaos had a major effect on both the Cavaliers' on-court performance and lack of local support, going 28–54 in 1980–81 (Stepien's first year as owner), followed by an abysmal 15–67 mark in 1981–82. The 1981–82 team lost its last 19 games of the season which, when coupled with the five losses at the start of the 1982–83 season, constitute the NBA's second all-time longest losing streak at 24 games. Stepien's penchant for trading away first-round picks came back to haunt him, as the eventual champion Los Angeles Lakers received Cleveland's first overall pick in the 1982 NBA draft, allowing them to select future Hall of Famer James Worthy. The trade in question took place in 1980, when Cleveland sent Butch Lee and a 1982 first-round pick to the Lakers for Don Ford and a 1980 first-round pick.

Although the team improved its record to 23–59 the following year, local support for the Cavaliers eroded which eventually bottomed out that year by averaging only 3,900 fans a game at the cavernous (and isolated) Coliseum which seated more than 20,000.

Though Stepien eventually threatened to move the franchise to Toronto and rename it the Toronto Towers - to the point that he had a Toronto Towers logo created - brothers George and Gordon Gund purchased the Cavaliers in 1983 and decided to keep the team in Cleveland (it would be another 12 years before Toronto finally got an NBA team in the form of the Raptors via expansion). As an incentive to the Gunds, NBA owners awarded the team bonus first-round picks for each year from 1983 to 1986 to help compensate for the ones Stepien traded away."Ted Stepien, N.B.A. Owner, Is Dead at 82" NY Times September 15, 2007

1983–1986: The Gunds take over Shortly after purchasing the Cavaliers in 1983, the Gunds (George and Gordon) changed the team colors from wine and gold to burnt orange and navy blue. Furthermore, they officially adopted "Cavs" as a shorter nickname for marketing purposes, as it had been used unofficially by fans and headline writers since the team's inception.

Under the coaching of George Karl, the Cavs failed again, and missed the playoffs, with a 28–54 record, in the 1983–84 season. The Cavs finally returned to the playoffs in 1985, only to lose to the eventual Eastern Conference Champion Boston Celtics in the first round. At that point, the team was in transition, led by dynamic players such as World B. Free, Roy Hinson and John Bagley. But in 1986, Karl was fired after 66 games. Interim head coach Gene Littles guided the team the rest of the way, which saw the Cavs finish one game short of the playoffs. During the seven-season period, the Cavs had nine head coaches: Stan Albeck, Bill Musselman, Don Delaney, Bob Kloppenburg, Chuck Daly, Bill Musselman (again), Tom Nissalke, George Karl, and Gene Littles. The only playoff appearance earned during this stretch was during the 1984–85 season under Karl, losing to the Boston Celtics in the first round in four games (1–3).

1986–1995: The Daugherty/Nance/Price era

During the 1986 NBA draft, the Cavs acquired Brad Daugherty, Mark Price, and Ron Harper. They would also add Larry Nance just before the 1988 trade deadline, in a deal with the Phoenix Suns. Those four players (until Harper was later traded to the Los Angeles Clippers in 1989 for the rights to Danny Ferry) formed the core of the team, under the direction of head coach Lenny Wilkens, that led the Cavs to eight playoff seasons in the next nine years, including three seasons of 50 or more wins.

In 1989, the Cavs were paired against the Michael Jordan-led Chicago Bulls in the first round of the playoffs. In the fourth game of the best-of-five-series, Cleveland managed to beat the Bulls in overtime 108–105 to level the series at 2–2. Home court advantage went to Cleveland. The game was evenly matched, until Cleveland managed to score on a drive and raise the lead by one, with three seconds left. Chicago called for a time-out. The ball was inbounded to Michael Jordan, who went for a jump shot. Cleveland's Craig Ehlo jumped in front to block it, but Jordan seemed to stay in the air until Ehlo landed. "The Shot" went in as time ran out, with Chicago winning the series 3–2. The pinnacle of the Cavs' success came in the 1991–92 season, when they compiled a 57–25 record and advanced to the Eastern Conference Finals, losing again to the Chicago Bulls, 4–2. Soon after, the Cavs entered into a period of decline. With the retirements and departures of Nance, Daugherty, and Price, the team lost much of its dominance and were no longer able to contest strongly during the playoffs. After the 1992–93 season, in which the Cavs had a 54–28 regular-season record but suffered an early exit from the playoffs in the Eastern Conference Semi-Finals to the Chicago Bulls, Wilkens left to coach the Atlanta Hawks.

Following the hiring of Mike Fratello as head coach starting with the 1993–94 season, the Cavs became one of the NBA's best defensive teams under the leadership of point guard Terrell Brandon. But the offense, which was a half-court, "slow-down" tempo installed by Fratello, met with mixed success. Although the Cavaliers made regular playoff appearances, they were unable to advance beyond the first round. In the 1994 NBA Playoffs, the last which Daugherty and Nance played in, the Cavs yet again met the Chicago Bulls in the first round, led by Scottie Pippen in the wake of Jordan's first retirement. The Bulls proved that it was not just the "Jordan Curse", and would prevail yet again by sweeping the Cavs 3–0 in the first-round encounter.

In 1994, the Cavs moved back to downtown Cleveland with the opening of the 20,562-seat Gund Arena. Known by locals as "the Gund", the venue served as the site of the 1997 NBA All-Star Game. The arena and the Cleveland Indians' Jacobs Field were built together as part of the city's Gateway Sports and Entertainment Complex

1995–2003: Near decade of struggles

Mike Fratello years

Due to serious back injuries, Brad Daugherty was forced to retire in 1996 after sitting out the 1994–95 season. Larry Nance had also retired following the 1993–94 season, and Mark Price was traded to the Washington Bullets after the 1994–95 season. The Cavs under Brandon would lose to the New York Knicks in the first round of both the and playoffs. Then on April 20, 1997, the Cavs lost a virtual winner-take-all game to the Bullets on the final day of the regular season, denying them a playoff berth.

The Cavs revamped their starting lineup during the 1997 off-season, sending guard Bobby Phills, and forward Chris Mills to free agency, and trading Terrell Brandon and Tyrone Hill to the Milwaukee Bucks as part of a three-team trade. They acquired All-Star forward Shawn Kemp from the Seattle SuperSonics (from the three-team trade involving Cleveland, Seattle and Milwaukee) and guard Wesley Person from the Phoenix Suns. Later on, players like Kemp and Žydrūnas Ilgauskas added quality to the team, but without further post-season success. The Cavs did have five All-Stars/All-Rookies in 1998 with Kemp a starting All-Star for the East, Brevin Knight and Ilgauskas on the All-Rookie First Team, and Cedric Henderson and Derek Anderson on the All-Rookie Second Team. No other NBA team has ever been represented by five players at the All-Star celebration or four players as All-Rookies in the same year. Still, in the three seasons that Kemp played for the Cavs, they managed only one playoff appearance and one playoff win. Fratello was fired following the shortened 1998–99 season.

Early 2000s struggles