He was cremated with state honours at his residence at Kuruchithanam in the district.
Chief Minister Pinarayi Vijayan, Ministers Kadanapally Ramachandran, C Raveendranath, Thomas Chandy, Mathew T Thomas, CPI State Secretary Kannam Rajendran and LDF convener Vaikom Viswam were among those present on the occasion.
Vijayan was 60 and is survived by wife and two daughters.
Hailing from Uzhavoor in Kottayam district, Vijayan began his political career during his college days as a leader of the Kerala Students Union (KSU), the student wing of the Indian National Congress.
Vijayan, known for his speech containing political wits, later joined the NCP and rose to the rank of its state president.
He also emerged as a key member of the LDF state committee during the Assembly polls held last year.