Even in his early years, Krishna Iyer was influenced by the socio-economic problems confronting the common people and involved in uplifting them. In 1948, authorities jailed him on charges of giving legal aid to the communists.

In the year 1952, he was elected to Madras Legislative Assembly from Koothuparambu. In the assembly, he proved successful in making changes in Malabar Agrarian Relations Bill to protect the welfare of tillers.

In 1957, Krishna Iyer was elected to the Kerala Legislative Assembly from Thalassery Assembly Constituency. He was included in the EMS ministry and was assigned the administration of Home, Law, Jail, Irrigation, Electricity and Social Welfare.

In the interim elections in 1960, he was again elected. He failed in the 1965 General Elections and gradually withdrew from active politics.