Both players will be on a major league roster for the first time.
"I'm beyond excited. It is a dream come true," said Cingrani, who hadn't had a chance to call home with the news.
"It is unbelievable for me and Billy. I played with Billy a lot" in the minors. "It will be unbelievable for both of us."
Cingrani found out earlier that he will start the second game of the season against St. Louis on April 2. It's his first time on an opening-day roster.
The 24-year old left-hander allowed one run and five hits, including a homer by Nick Evans. Cingrani walked one but picked off two runners.
"Cingrani is the confident kind. He's not emotionally fragile," Reds first-year manager Bryan Price said.
Hamilton also singled. The speedster is expected to be in the opening day lineup, leading off in center field.
Hamilton almost hit his second homer of the spring. His drive bounced high off the wall and got past right fielder Jordan Parraz, and Hamilton took a wide turn at third but held.
On-deck batter Brandon Phillips was jumping up and down, waving on Hamilton.
"He's been terrific," Price said. "His approach has been impeccable. He has kept the ball out of the air except for two sacrifice flies he hit the other day. His defense has been impeccable, too."
Randall Delgado, hoping for a place in the Diamondbacks' rotation, pitched four innings and gave up two runs and seven hits.
"It was good today," Delgado said.
The Diamondbacks optioned Archie Bradley, one of the candidates to start to the minor leagues this morning.
"I'm just waiting for the manager to tell me what's going on. I'm not in a rush for it," Delgado said.
Diamondbacks: Delgado got two outs against the Dodgers on March 23 in Australia in his previous appearance. He made three spring training starts before the trip to Australia for a pair of regular-season games.
Delgado struck out three and walked one against the Reds. He struck out three.
Reds: Cingrani allowed 15 earned runs in 24 1/3 innings in six spring starts.
"Statistically, it hasn't been a good spring, but he has improved his changeup and breaking ball," Price said.
Reds: Catcher Devin Mesoraco hasn't played in 10 days because of a strained oblique.
"Devin has to play. He has to catch, throw, hit and run. It is unlikely that he will join us but we haven't signed off on putting him on the disabled list," Price said.
Brett Marshall is slowed by a strained tendon in his middle finger. He strained it in the game on Wednesday against the White Sox. "Marshall is seeing a hand specialist in Phoenix today," Price said.
"There are a lot of balls in the air. We've discussed it already, just trying to figure out what to do with the 40-man roster," Price said.
The Reds play against their minor league affiliates in Pensacola on Friday night and Louisville on Saturday afternoon.