Smith was activated off the 15-day injured list by the Mets on Tuesday, Tim Healey of Newsday reports.
Smith has been held out of action since the end of July with a lat strain on his right side. During his rehab stint in Triple-A Syracuse, he pitched four scoreless innings, giving up just three hits and striking out six batters. He figures to serve as a middle-innings option in the Mets' bullpen as they prepare for what they hope will be a deep run into the postseason.