Rajam Krishnan was born in Musiri, Tiruchirapalli district. She had very little formal education and appears to have been largely an autodidact.
She started publishing in her twenties. She is known for writing well researched social novels on the lives of people usually not depicted in modern Tamil literature - poor farmers, salt pan workers, small-time criminals, jungle dacoits, under-trial prisoners and female labourers. She has written more than 80 books. Her works include forty novels, twenty plays, two biographies and several short stories. In addition to her own writing, she was a translator of literature from Malayalam to Tamil.
In 1973, she was awarded the Sahitya Akademi Award for Tamil for her novel Verukku Neer. In 2009, her works were nationalised by the Government of Tamil Nadu.