"I recently stepped down from Uber's board given the overlap between the two companies," Drummond said in an email statement to Business Insider.
He called Uber a "phenomenal" company and said that Google Ventures remains an "enthusiastic investor" in Uber, while Uber and Google will continue to be partners.
Google confirmed to Business Insider that Drummond has been off the board for a while, but didn't give a specific date.
Drummond joined the board when Alphabet's investment arm, Google Ventures (now GV), poured a reported $300 million into Uber in 2013.
In the last year, both companies have put increased focus on their self-driving car efforts. Uber is also developing its own digital maps, in order to lessen its reliance on Google's maps.
Uber CEO Travis Kalanick said in a statement that Drummond has "been a sage advisor and a great personal friend. I wish David and Alphabet the best, and look forward to continued cooperation and partnership."
The Information's Amir Efrati previously reported that Drummond wasn't attending board meeting.