The Japanese right-hander threw 25 pitches Monday.
''As for the first time, I think it went well,'' Tanaka said through an interpreter.
Tanaka missed 2 1/2 months last season with a partially torn ulnar collateral ligament in his right elbow.
''I tried not to go too hard today,'' Tanaka said. ''The reason is, it's natural once you get on the mound and once you're facing batters you want to go hard. That's what I was thinking on the mound.''
Tanaka said there have been no issues with the elbow.
''I understand that everybody's worried about the elbow and I understand too that I have to be cautious about it as well, but so far it's been good,'' Tanaka said.
Tanaka threw five or six split-finger fastballs.
''I'm pretty satisfied with how the ball was moving,'' he said.
Tanaka will likely throw batting practice again or take part in a simulated game later this week.