Treinen back to the Athletics, along with Sheldon Neuse and Jesus Luzardo, for Sean Doolittle and Ryan Madson. At the time of the trade he was 0–2 with a 5.73 ERA and three out of five in save opportunities converted over 37 appearances. As the Athletics' closer, he converted 13 of 16 save opportunities after the trade. In early September, Treinen took three losses in a row, and was on the hook for a fourth, but the A's rallied for two runs in the bottom of the ninth to walk off the Houston Astros 9-8, and Treinen got the win instead. Treinen recorded 13 saves with the A's in 2017, including his last 12 opportunities in a row after blowing three of his first four. In the first half of the 2018 season, Treinen had a 5–1 record with an 0.79 ERA and 23 saves. He was named an All-Star. He finished the season with a 9-2 record, 38 saves (3rd in the AL), and an 0.78 ERA. Treinen and the Athletics went into salary arbitration before the 2019 season, and Treinen won, earning a $6.4 million salary for the season. On June 21, 2019, Treinen was placed on the 10-day injured list with soreness in his right shoulder after an appearance against the Tampa Bay Rays in which he gave up three runs without recording an out. He was activated on July 3, after which he ceded the role of closer to Liam Hendriks. In 2019 he was 6-5 in 57 relief appearances with 16 saves and a 4.91 ERA, as he struck out 59 batters in 58.2 innings. On December 2, Treinen was non-tendered by Oakland and became a free agent. Los Angeles Dodgers (2020–present) On December 15, 2019, Treinen signed a one-year, $10 million contract with the Los Angeles Dodgers. The start of the 2020 season was delayed to late July by the COVID-19 pandemic, but Treinen appeared in 27 games for the Dodgers (3rd in the NL), with a 3–3 record with one save and a 3.86 ERA. In the postseason, he pitched one inning in the Wild Card series, innings in the 2020 NLDS, innings in the 2020 NLCS and innings in the 2020 World Series, allowing six total runs and picking up a save in Game 5 of the World Series. The Dodgers won the championship in six games After the season, the Dodgers