Moideen (75) was taking treatment for cancer for the past six years.
He leaves his wife and four sons, sources said.
A two time MLA representing Beypore assembly constituency in Kozhikode in 1977 and 1980, Moideen was also the KPCC General Secretary in 1975 under the presidentship of A K Antony.
He was also the Deputy Leader of the Congress Legislature Party in 1980 under the leadership of Oommen Chandy, the present Chief Minister.
The funeral will be held here tomorrow.