Born in a middle-class family to Krishnan and Uma Krishnan in Kerala, the Tamil Iyer actress got her early education from Church Park School and pursued her higher education in Ethiraj College, Chennai. Later, she modelled and won Miss Salem in 1999, Miss Chennai in 1999 and Miss India Miss Beautiful Smile in 2001. In school, she participated in several cultural activities, sports and school band. Trisha is said to be a good ballet dancer. She studied in the same school as former Tamil Nadu Chief Minister J.Jayalalitha.
Trisha first made her debut in films when she was offered a small cameo in the film Jodi. However, the first movie in which she signed up to enact the role of the leading lady was Priyadarshan's Leysa Leysa. A string of flops marked the beginning of her career, such as Manasellam,and Alai. However she was well suited for her role opposite Surya in Mounam Pesiyadhe and won critical acclaim.