She delivered the news at a company meeting Friday, according to Tech in Asia. Calls to a Grab Vietnam media spokesperson went unanswered.
It is unclear who will take over as the new chief.
Van had joined the company in November 2019 after 17 years at Unilever Vietnam, and was appointed managing director in February 2020.
She took over from Jerry Lim, who returned to a Singapore-based role as regional head of customer experience.
On March 10, Grab increased all fares in Vietnam amid the surging gasoline prices.