Senga was born in Gamagori, Aichi Prefecture, where he started playing rubber-ball baseball as a third baseman until he graduated from middle school, then switched from third baseman to pitcher due to the manager of Gamagori High School baseball club, who saw the quality of Senga's throwing fitting more as a pitcher.

Although Senga and his team never made it to either Japanese High School Baseball Championship or Japanese High School Baseball Invitational Tournament in Koshien Stadium, the owner of a sporting goods store in Nagoya recommended Senga to Kazuo Ogawa, then-the scout manager of Fukuoka Softbank Hawks, as a potential player to be drafted.

On April 23, 2012, he signed a 4.4 million yen contract with the Fukuoka SoftBank Hawks as a registered player under control.

In the 2015 season, Senga pitched in the Pacific League in August, partly due to the rehabilitation of his right shoulder.

On August 19, he got his first win as a starting pitcher,[13] finishing the regular season with 4 Games pitched, a 2–1 Win–loss record, a 0.40 ERA, and 21 strikeouts in 22.1 innings.

He earned his first career victory after pitching 5 1/3 innings, giving up one run and striking out eight in a 5-1 Mets win.

[39] On May 17, Senga struck out 12 batters in a game against the Tampa Bay Rays, setting a new Mets franchise record in strikeouts by a Japanese pitcher.

[40] He was named to the 2023 National League All-Star team on July 8, replacing Marcus Stroman of the Chicago Cubs.

[41] On September 27, during a game against the Marlins, Senga recorded his 200th strikeout of the season, becoming the first Mets rookie since Dwight Gooden to accomplish the feat.

[42] In Senga's stellar rookie season, he made 29 starts for the Mets, posting a 12-7 record, a 2.98 ERA, and 202 strikeouts across 1661⁄3 innings pitched.

[45] 2024 On February 22, 2024, the Mets announced that Senga had been diagnosed with a moderate posterior capsule strain in his throwing shoulder and would begin the season on the injured list.

[47] Senga was activated from the injured list on July 26 and made his first start of the season that evening against the Atlanta Braves.

[48] On September 22, Mets manager Carlos Mendoza announced that Senga would be officially shut down for the remainder of the season.

[49] However, on October 4, it was announced that he would be the Game 1 starter in the 2024 National League Division Series against the Philadelphia Phillies, scheduled for the following night.

[56] He became a gold medalist by beating the United States in the final round, allowing no runs in two games.