Dominguez, who signed a free agent deal in mid-February, made the Reds' 25-man roster for opening day. The Reds open at home on Monday at home against the Pirates.
"I have great emotions, obviously. I was happy for my family and myself for sticking through it and the organization for giving me the opportunity," Dominguez said in a story posted on the Cincinnati Reds website.
Dominguez played a team-high 25 games in the spring and hit .316 with three home runs and 14 RBIs in 57 at-bats. He's played five positions in the past two years, including first base, third base, shortstop, left field and right field.
He made his major league debut in 2014 with the San Francisco Giants, going 1-for-17 with a home run and two RBIs in eight games. He was a third-round Draft pick in 2009.