Domínguez signed with the Phillies as an international free agent in 2011, and made his MLB debut in 2018.

[2] He made his professional debut in 2012 with the DSL Phillies and spent the whole season with them, going 4–4 with a 3.48 ERA and 40 strikeouts in 671⁄3 innings in 15 games (11 starts).

[7] He began 2018 with the Double-A Reading Fightin Phils, going 1–2 with a 2.08 ERA with 18 strikeouts in 13 innings in 8 games, averaging 12.5 strikeouts per 9 innings, and was promoted to the Triple-A Lehigh Valley IronPigs in late April for whom he was 1–0 with a 0.00 ERA in 3 games.

[1] Between the two minor league teams, in 162⁄3 innings Domínguez gave up 8 hits and 2 walks, and struck out 21 batters.

[20] His season ended early with him on the injured list, due to a damaged ulnar collateral ligament in his right elbow.

[21] Dominguez underwent Tommy John surgery on July 30, 2020, more than a year after he was initially placed on the injured list.

On February 17, 2021, Dominguez was placed on the 60-day injured list as he continued to recover from Tommy John surgery.

In the 2022 regular season, he was 6–5 with nine saves and a 3.00 ERA, as in 54 innings he struck out 61 batters over 54 relief appearances.

He pitched in 9 games during the 2022 postseason, allowing 2 earned runs and striking out 18 hitters in 10+2⁄3 innings.

On July 26, 2024, Domínguez was traded to the Baltimore Orioles alongside Cristian Pache in exchange for Austin Hays.