The right-hander turns 25 later this year. News of the agreement broke on Jan. 12, but Sierra was waiting on his visa.
"It's a complicated process. It's just going to take time, and there's not a ton of transparency to how that works in terms of timing," Dodgers president of baseball operations Andrew Friedman said on Jan. 30. "We're hopeful to have him in spring training when pitchers and catchers report."
Sierra had a 4.23 ERA in five years in La Serie Nacional in Cuba, with 221 strikeouts and 166 walks in 300 innings for Holguin and Sancti Spiritus. He started 25 of his 131 career games in Cuba, though in the 2014-2015 season all 36 of his appearances came in relief.
In his final season in Cuba, Sierra had a 6.10 ERA in 62 innings, with 55 strikeouts and 31 walks, though nine of the walks were intentional. He also had 11 wild pitches and seven hit by pitches. He hit 38 batters in his last three seasons.
Beginning with outfielder Yasiel Puig in 2012, the Dodgers have been the most active MLB team in signing Cuban players. The $30 million committed to Sierra trails the $62.5 million committed to infielder Hector Olivera in 2015 (though he was traded before reaching the majors, with the Dodgers on the hook for $29.2 million) and the $42 million given to Puig. Other free agents include Alex Guerrero (four years, $28 million) and Erisbel Arruebarrena (five years, $25 million), both signed in 2014.
The Dodgers also signed pitcher Pablo Fernandez to a minor league contract in 2015, with an $8 million bonus.
In the 2015-2016 international signing period the Dodgers have invested heavily in Cubans in the amateur market as well, with $16 million to pitcher Yadier Alvarez, $15.5 million to outfielder Yusniel Diaz, and $6 million to infielder Omar Estevez, each of those subject to a 100-percent tax for the Dodgers exceeding their allotted international bonus pool.
Sierra takes the open 40-man roster spot created by Frankie Montas being placed on the 60-day disabled list.