Atlanta selected Hamilton's contract from Triple-A Gwinnett on Thursday.
Hamilton didn't make the Opening Day roster after inking a split contract over the offseason, but he'll get a look with the big club now after allowing two runs with a 9:1 K:BB over his first 6.1 innings at Gwinnett. The 30-year-old has typically been pretty effective when healthy, authoring a 3.45 ERA and 152:62 K:BB over the last three seasons with the Yankees. He'll work in middle relief.