Siverio, 25, most recently played for the Águilas de Mexicali of the Mexican Pacific League last winter. He went 3-1 with a 2.45 ERA and 36 strikeouts in six starts.
Siverio completed his physical in Seattle two weeks ago before the deal was finalized. He will take part in the Mariners' mini-camp in February.
“This is a proud moment for me, to be able to join the Seattle Mariners who have several Cubans in the organization that are my compatriots,” Siverio said via MLBlogs.com. “I feel very happy because of the way that I have been treated here in Seattle and now the only thing left to do is to do my part, work hard and reach the Major Leagues.”
Before leaving Cuba, Siverio played six seasons for Villa Clara in the Cuban National Series from 2007-12 and posted a 3.24 ERA. In August, he worked out in a showcase for 20 MLB teams. He also held an earlier showcase in June.
According to Kiley McDaniel of Fangraphs.com, Siverio received a $275,000 bonus and a split contract that will pay him $508,000 in the majors or $120,000 in the minors. It's currently unclear where in the Mariners' organization Siverio will begin his career.
Jorge Ebro of the El Nuevo Herald first reported Siverio's signing in November.
- Mike Fiammetta