Darvish threw 55 pitches, including warmups, before the game with the San Diego Padres at Wrigley Field. The right-hander has been on the disabled list since late May with triceps and elbow injuries.
"All my pitches, velocity-wise, were up there at their highest and then I was able to follow through with my arm," he said through a translator.
Darvish said he hopes to face batters in a simulated game in his next outing. He has made just eight starts for the Cubs this season, going 1-3 with a 4.95 ERA after signing a six-year, $126 million contract in the offseason.
Darvish said he began to feel better after getting treatment on his back about 10 days ago.
"Treatment-wise, I switched from treating the elbow to the spine, the back, and that triggered a more positive level," he said. "Everything up until that point there was pain and discomfort involved. I was just trying to see alternatives."
Darvish initially began throwing a few weeks after going on the DL, but had to be shut down in late June when he felt pain.
He said he's confident there will be no setbacks this time. "Now that I'm pitching, I'm very optimistic," he said.
Earlier this week, Joel Wolfe, Darvish's agent, told The Athletic that he was not happy with "classless" comments about Darvish by commentator Alex Rodriguez during ESPN's Sunday Night Baseball.
Rodriguez accused Darvish of being a distraction to the Cubs, but Darvish brushed off the comments and said he "still has a lot of respect for A-Rod."
When asked Saturday if he has heard from Rodriguez since the comments, Darvish used the opportunity to lighten the situation.
"If he sends me a text message or something, I'll keep it and maybe take a screenshot and then print it out and frame it just for a keepsake," Darvish said through a translator.
After some laughter, a smiling Darvish switched to English: "I'm not joking."
The Associated Press contributed to this report.