'Ichiro's Theme' is a homage to US baseball player Ichiro Suzuki, who was traded to the New York Yankees after 12 years with Gibbard's Seattle Mariners on Monday.
"I wrote this a few years ago," Gibbard said. "Today seems like the best day to let you all hear it. Thank you, Ichiro."
Gibbard announced plans to release his first solo studio album last week.
The Death Cab for Cutie frontman will bring out Former Lives on October 15.