The star Japanese rookie struggled to complete four laps of the practice field, not much more than a mile, at Tampa, Florida.
"Just the running part, that was really hard for me today," Tanaka told reporters through an interpreter. "I actually didn't know that I was going to run this much. And I'm a little bit of a slow runner, so that part I really can't help."
Otherwise it was a solid start for Tanaka, who was mobbed by Japanese media.
He threw 32 pitches to catcher Francisco Cervelli and participated in a variety of spring training exercises, according to MLB.com.
"As a player, I feel very honored to get this much attention," Tanaka said. "Some fans were cheering today and I was very happy to receive those cheers.
"But at the same time, I understand that I haven't given out any results on the field yet. So my focus is to train and go out there and try to get those results."
The Yankees won the race to lure Tanaka, 25, to the major leagues, signing him for $155 million over seven years.
He is coming off a triumphant season in Japan, where he helped the Rakuten Eagles clinch the national championship, finishing the year with a flawless 24-0 record and a 1.27 earned run average.