At the age of 20, Karunanidhi went to work for Jupiter Pictures as a script writer. His first film Rajakumari, gained him much popularity. It was here that his skills as a script writer were honed. He wrote more than 70 screenplays including

• Rajakumari
• Abimanyu
• Mandiri Kumari
• Marutha Naattu Ilavarasi
• Manamagan
• Devaki
• Parasakthi
• Panam
• Thirumbipaar
• Naam
• Manohara
• Ammaiappan
• Malai Kallan
• Rangoon Radha
• Raja Rani
• Puthaiyal
• Pudhumai Pithan
• Ellorum Innattu Mannar
• Kuravanchi
• Thayillapillai
• Kanchi Thalaivan
• Poompuhar
• Poomalai
• Mani Makudam
• Marakka Mudiyuma?
• Avan Pithana?
• Pookkari
• Needhikku Thandanai
• Paalaivana Rojakkal
• Pasa Paravaikal
• Padadha Theneekkal
• Niyaya Tharasu
• Pasakiligal
• Paasaparavaigal
• Kannamma