Jesia was born into a Parsi family in 1969.
Mehr was discovered in 1986 when photographer Faroukh Jussawalla suggested that she take part in the Miss India contest. A week later she took the title, and went on to represent her country in the Miss Universe 1986 pageant. As part of a sponsorship deal, Mehr had to work with Bombay Dyeing for a year after the contest at no charge. She has attributed much of her career trajectory since that first year to Mickey Contractor. According to her, "He never let me look the same in any two campaigns.". Her first ad film was for Lakme's winter creme campaign. Her other campaigns include Vimal, Bombay Dyeing, OCM, Nivea, Palmolive, Gleem, Forhans, Philips and Campa Cola.
Mehr and Arjun Rampal produced the film I See You (released on 29 December 2006) through their production company Chasing Ganesha. The film starred Arjun Rampal, Vipasha Agarwal, Sonali Kulkarni and Boman Irani.