Dhanak, who joined the company 18 months ago from Shine Communications, will assume day-to-day running of the agency across both the UK and EMEA, reporting to CEO Frankie Cory.
She fills a role left vacant since Mandy Sharp went on maternity leave last October and did not return to the agency.
Cory said: "Misha has made a significant impact to the agency since joining, including two PRWeek Award nominations and growth across the agency."
The move follows the recent addition of planning director Gemma Hopkin and creative director Joe Sinclair to the agency.
Dhanak said, "I’m incredibly proud of what Citizen has achieved in the past few months and look forward to helping shape our continued growth, both in the UK and across the EMEA region."