Mohanty replaces Roopam Garg who is being re-located to ZenithOptimedia's London office to take on a global role.
Deboo has more than 15 years' experience in India and Vietnam and has been leading the Unilever operations for Mindshare Vietnam over the past four years.
On the appointment, Phil Talbot, CEO Asia-Pacific of ZenithOptimedia, said, "Deboo has a great track record and understanding of the Vietnam market place. It was clear to me he was ready for the challenge of a leadership role across our operation in Vietnam."
Mohanty stated, "The opportunity fits in well with my career progression and in a dynamic market like Vietnam, there is a lot to contribute in the field of advertising and marketing investment management."
VivaKi in Vietnam is the combined operations of ZenithOptimedia and Starcom. In last two years, the Publicis Groupe entity has consolidated its dominance in the local market by doubling its billings.
Last year, Equinox, a division of ZenithOptimedia, was launched to handle an extended client base. In-sight DNA 2.0, a Zenith proprietary tool on consumer, brand and media, covering 12 markets in Vietnam, was also started.
Mohanty's appointment follows the appointment of Venus Navalta as chairman of ZenithOptimedia Philippines earlier this month.