She was born in Mananthavady, Wayanad district, to Kuttikrishnan Nair and Yashoda. Thankam Mohan's primary education was at G H S Mananthavady and Gov College Mananthavady. She has a Master's degree in Theatre Arts from Thrissur School of Drama.

Thankam Mohan started her acting career through theatre. In 2008, Thankam entered the film industry with the film Chandranilekakoru Vazhi directed by Biju Varkey. She then acted in more than ten films including Kamukuri, Jan.A.Man and Paltu Janvar. Apart from films and theatre, Thankam Mohan has also acted in several short films. Her performance in the web series Kochamerika, a short, brought her to prominence. After that, Thankam Mohan's roles in Karik Flick's Sebastian's Friday and Parakkum Pankajam were noticed.

Thankam Mohan's husband: Mohan Krishnan (playwright, director, actor. Has done small roles in movies and short films) Eldest son Jishnu Mohan is a film actor. Second son Vishnu Mohan.