Per ESPN's Jeff Passan, Treinen had multiple offers on the table prior to reaching agreement with the Dodgers for $10 million.
Treinen became a free agent on Dec. 2 when the Oakland Athletics decided not to tender him a contract coming off a rough 2019.
Per MLB Trade Rumors, Treinen was projected to earn $7.8 million through arbitration if he had remained with the A's next season.
Oakland's decision to non-tender Treinen capped off a steep one-year fall for the 31-year-old. He was an All-Star in 2018 and finished sixth in American League Cy Young voting after posting a 0.78 ERA with 38 saves, 100 strikeouts and 46 hits allowed in 80.1 innings.
Last season saw Treinen's ERA balloon to 4.91 with a 1.619 WHIP in 57 games.
The Dodgers had the fourth-lowest bullpen ERA in MLB last season (3.78), but only one of their top six relievers by appearances had an ERA under 3.50.