Waltrip drove the No. 15 NAPA Chevrolet for the past five seasons, winning four times, including the 2001 and 2003 Daytona 500s.
Through 18 events this year, he is 19th in the points standings with no wins and seven top-10 finishes.
Waltrip and Dale Earnhardt Jr. have had their differences this season. They came to a head when "Junior" ran into the back of Waltrip at the Coca Cola 600 Memorial Day weekend and knocked him out of the race.
"My professional relationship with DEI is ending, but my personal relationships have ties that are deep-rooted," Waltrip said. "Therefore, my decision to leave DEI is a difficult one. Our individual visions for the future are taking different courses."