On August 7, 2007, the Yankees purchased Chamberlain's contract, elevating him to the major leagues for the first time in his career.
In his debut, a Yankees victory over the Toronto Blue Jays, Chamberlain struck out the first batter he faced and went on to pitch two scoreless innings, striking out two.
Chamberlain's usage in games was initially restricted by what were referred to as the "Joba Rules", which prevented him from pitching on consecutive days and gave him an additional day of rest for each inning pitched in an outing.
On August 30, 2007, during a game against the Boston Red Sox, Chamberlain threw two pitches over the head of Kevin Youkilis.
Chamberlain was subsequently ejected for the first time in his Major League career.
The next day, Chamberlain was sentenced to a two-game suspension and a $1,000 fine.

In Game 2 of the 2007 ALDS against the Cleveland Indians, Chamberlain was pitching in the bottom of the eighth with the Yankees leading 1–0.
Suddenly, a host of small midges swarmed the field.
He was repeatedly sprayed down with insect repellent, which had no apparent deterrent effect on the midges.
Chamberlain threw 2 wild pitches, yielding the tying run.
The Indians went on to win the game 2–1.
The Yankees would then lose the Division Series against the Indians in 4 games in the best-of-five series.

On March 20, 2008, the Yankees announced that Chamberlain would start the season in the bullpen.
Manager Joe Girardi stated that Chamberlain would be used 'without restrictions' but that the team's use of Chamberlain would be guided by common sense.

Chamberlain was granted a leave of absence on April 13, 2008, when he received news that his father, Harlan, was in the hospital after collapsing at his home in Lincoln, Nebraska.
 At the time of his leave, Joba had a record of 1–0, with a 0.00 ERA, six strikeouts, and 3 holds in 4 games and 5​¹⁄₃ innings pitched.

Chamberlain returned from the bereavement in time for the 2nd game against the Baltimore Orioles on April 19, 2008.
On April 20, Hank Steinbrenner announced that he wanted Chamberlain to be moved into the rotation.

In May, Girardi announced Chamberlain was being transitioned into the starting rotation.
On June 3, Chamberlain made his first MLB start against Roy Halladay and the Toronto Blue Jays lasting only 2​¹⁄₃ innings while allowing 2 runs, a hit and 4 walks.
On June 25, Chamberlain earned his first career win as a starter, throwing 6​²⁄₃ scoreless innings against the Pittsburgh Pirates, en route to a 10–0 Yankees victory.

On July 25, Chamberlain threw 7 shutout innings against the Red Sox, outdueling Red Sox ace Josh Beckett, allowing only 3 hits and striking out 9.
The Yankees won the game 1–0.

On August 4, Chamberlain injured his shoulder in a game against the Texas Rangers and was placed on the 15-day disabled list with rotator cuff tendinitis.
Yankees General Manager Brian Cashman later acknowledged that this injury had a lasting effect.

Chamberlain ended the season with a 3–1 record and eight no-decisions.
On August 7, 2007, the Yankees purchased Chamberlain's contract, elevating him to the major leagues for the first time in his career. In his debut, a Yankees victory over the Toronto Blue Jays, Chamberlain struck out the first batter he faced and went on to pitch two scoreless innings, striking out two. Chamberlain's usage in games was initially restricted by what were referred to as the "Joba Rules", which prevented him from pitching on consecutive days and gave him an additional day of rest for each inning pitched in an outing. On August 30, 2007, during a game against the Boston Red Sox, Chamberlain threw two pitches over the head of Kevin Youkilis. Chamberlain was subsequently ejected for the first time in his Major League career. The next day, Chamberlain was sentenced to a two-game suspension and a $1,000 fine.
In Game 2 of the 2007 ALDS against the Cleveland Indians, Chamberlain was pitching in the bottom of the eighth with the Yankees leading 1–0. Suddenly, a host of small midges swarmed the field. He was repeatedly sprayed down with insect repellent, which had no apparent deterrent effect on the midges. Chamberlain threw 2 wild pitches, yielding the tying run. The Indians went on to win the game 2–1. The Yankees would then lose the Division Series against the Indians in 4 games in the best-of-five series.
On March 20, 2008, the Yankees announced that Chamberlain would start the season in the bullpen. Manager Joe Girardi stated that Chamberlain would be used 'without restrictions' but that the team's use of Chamberlain would be guided by common sense.
Chamberlain was granted a leave of absence on April 13, 2008, when he received news that his father, Harlan, was in the hospital after collapsing at his home in Lincoln, Nebraska.  At the time of his leave, Joba had a record of 1–0, with a 0.00 ERA, six strikeouts, and 3 holds in 4 games and 5​¹⁄₃ innings pitched.
Chamberlain returned from the bereavement in time for the 2nd game against the Baltimore Orioles on April 19, 2008. On April 20, Hank Steinbrenner announced that he wanted Chamberlain to be moved into the rotation.
In May, Girardi announced Chamberlain was being transitioned into the starting rotation. On June 3, Chamberlain made his first MLB start against Roy Halladay and the Toronto Blue Jays lasting only 2​¹⁄₃ innings while allowing 2 runs, a hit and 4 walks. On June 25, Chamberlain earned his first career win as a starter, throwing 6​²⁄₃ scoreless innings against the Pittsburgh Pirates, en route to a 10–0 Yankees victory.
On July 25, Chamberlain threw 7 shutout innings against the Red Sox, outdueling Red Sox ace Josh Beckett, allowing only 3 hits and striking out 9. The Yankees won the game 1–0.
On August 4, Chamberlain injured his shoulder in a game against the Texas Rangers and was placed on the 15-day disabled list with rotator cuff tendinitis. Yankees General Manager Brian Cashman later acknowledged that this injury had a lasting effect.
Chamberlain ended the season with a 3–1 record and eight no-decisions.
Joba Chamberlain