Born into a working-class family in Katlakalns Parish (now Ķekava Municipality) in the Governorate of Livonia, Kalnbērziņš joined the Bolshevik Party in April 1917.

He graduated from the Communist University of the National Minorities of the West in 1931 and from the Institute of Red Professors in 1933.

During World War II he was a member of the Military Council of the North-Western Front.

[2] After the defeat of the National Communist faction of the CPL in 1959 he was removed from his position of first secretary in May 1959.

Kalnbērziņš was retired in 1970 by the decision of the Council of Ministers of the USSR and received a personal pension.