Karunanidhi is known for his contributions to Tamil literature. His contributions cover a wide range: poems, letters, screenplays, novels, biographies, historic novels, stageplays, dialogues and movie songs. He has written Kuraloviam for Thirukural, Tholkaappiya Poonga, Poombukar, as well as many poems, essays and books. Apart from literature, Karunanidhi has also contributed to the Tamil language through art and architecture. Like the Kuraloviyam, in which Kalaignar wrote about Thirukkural, through the construction of Valluvar Kottam he gave an architectural presence to Thiruvalluvar, in Chennai, Tamil Nadu. At Kanniyakumari, Karunanidhi constructed a 133-foot-high statue of Thiruvalluvar, which portrays his feelings about the scholar. The books written by Karunanidhi's include Sanga Thamizh, Thirukkural Urai, Ponnar Sankar, Romapuri Pandian, Thenpandi Singam, Vellikizhamai, Nenjukku Needhi, Iniyavai Irubathu and Kuraloviam. His books of prose and poetry number more than 100.
Karunanidhi's stage plays include: Manimagudam, Ore Ratham, Palaniappan, Thooku Medai, Kagithapoo, Naane Arivali, Vellikizhamai, Udhayasooriyan and Silappathikaram. At the age of 20, Karunanidhi went to work for Jupiter Pictures as a scriptwriter. His first film, Rajakumaari, gained him much popularity. It was here that his skills as a scriptwriter were honed. He wrote 75 screenplays including: Rajakumaari, Abimanyu, Manthiri 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, Kannamma, Uliyin Osai, Pen Singam,Ilaignan and Ponnar Shankar.