Blevins has pitched parts of 13 seasons with four different teams. He's spent time with the A's, Nationals, Mets and Braves.
Last season with Atlanta, the 36-year-old posted a 3.90 ERA and 37 strikeouts in 32.1 innings over 45 appearances.
Blevins appears to be another low-risk, high-reward signing by the Giants' front office. If he makes the team out of spring training and shows that he has value, he could be a prime trade candidate ahead of the July 31 trade deadline.