Main Actor Nahin Hoon follows the emotional journey of Adnan Baig (Nawazuddin Siddiqui), a retired bank executive who finds himself battling loneliness, anxiety, and a sense of emptiness after stepping away from a long corporate career. When his daughter Nazia (Meenakshi Arundhati) learns that he once performed in theatre during his college days, she encourages him to rediscover his passion for acting. Soon, Adnan gets an opportunity to audition for a role with a Frankfurt-based production house through an online session with Mouni (Chitrangada Satarupa), a talented acting coach living in Mumbai. Though initially hesitant and dismissive, Mouni eventually agrees to mentor him. As their virtual acting lessons progress, Adnan is forced to confront long-buried memories, emotional scars, and personal truths, realizing that acting is not merely performance, but a deep exploration of the human mind and soul.