The Venezuelan leftie is reported to be joining the AL East outfit until 2031.
He debuted for the Phillies in 2018 and started slowly before joining the rotation. Last year, he produced a 3.20 ERA, his second-best season to date.
It comes after the Red Sox missed out on third baseman Alex Bregman, who signed with the Chicago Cubs on Monday, after he opted out of his deal with the Boston side.
Suarez has been an all-star in 2024 and has been to the playoffs four times.