This followed a meeting between the 96-year-old Gowri and CPI-M state secretary Kodiyeri Balakrishnan at the former's residence.
Gowri is the only surviving member of the country's first Communist government that took power in Kerala in 1957 under the leadership of the legendary E.M.S. Nampoodiripad.
She has contested all the assembly elections since then, loosing only thrice. She was a minister five times -- four times as a CPI-M nominee and once, in 2001-06, in the Congress-led front.
The CPI-M sacked her in 1994, and she quickly formed her own party, the JSS, and allied with the Congress-led United Democratic Front (UDF).
While one faction of the JSS is still with the UDF, the other group led by her will now merge with the CPI-M.
The merger will take place on August 19, the birth anniversary of P. Krishna Pillai, a founder of the Communist movement in Kerala, Balakrishnan said.