The deal includes an invitation to major league spring training. He will make $1.8 million if he makes the major league roster, a source confirmed to ESPN.
The news was first reported by The Athletic.
Liriano, 35, pitched for the Detroit Tigers last season, going 5-12 with a 4.58 ERA in 133 2/3 innings pitched. He made 26 starts.
The 13-season veteran pitched previously with the Pirates from 2013 to '16. He was 41-36 with a 3.67 ERA in 107 starts during that span.