On September 8, 2019, his 29th birthday, Cole became the second pitcher ever to strike out 14 or more hitters in three consecutive games. On September 18, 2019, Cole struck out his 300th batter of the season, becoming the third Astros pitcher to strike out 300 batters in a single season, after J. R. Richard and Mike Scott. Cole became the second-fastest pitcher to register 300 strikeouts in terms of innings pitched. His 198 ⁄3 innings trails only Randy Johnson, who achieved the feat in 197 ⁄3 innings in 2001. The following start, September 24, 2019, Cole struck out 14 batters to break the single-season strikeout record for any Astros pitcher, bringing his total to 316 on the year, and allowing only two singles in his appearance of seven scoreless innings. In his next start on September 29, 2019, Cole set an MLB record with his ninth consecutive outings with at least 10 strikeouts.
On December 18, 2019, Cole signed a nine-year contract worth $324 million with the Yankees. Cole’s contract is the largest signed by a pitcher, topping the $245 million, seven-year contract signed by Stephen Strasburg. Cole’s contract has an average annual value of $36 million, which also represents the highest average annual value of any player contract in Major League Baseball, eclipsing the previous average annual value record set by Mike Trout, at an average annual value of $35.5 million. The contract also allows Cole to opt out and become a free agent again after the fifth year; however, if he attempts to do so, the Yankees can choose to prevent him from doing so by adding an additional year and $36 million to his contract, which would bring the total length and value of the contract to 10 years and $360 million.
Cole attended the 2001 World Series, of which the Yankees took part. He held a sign that said "YANKEE FAN TODAY TOMORROW FOREVER", and a photograph shared by Newsday went viral in 2019 when news of his signing with the Yankees was reported. He brought the sign to his introductory press conference with the Yankees.