Studied at the Leningrad Polytechnical Institute.
After working as an engineer, he rose through the ranks.
A Communist Party member from 1926, Kozlov rose slowly but steadily through the ranks, from secretary of the Ishevsk Party Committee (1940), to party organizer of the Kirov plant in Leningrad (1949), to first secretary of the Leningrad City Party Committee in 1950, when he was also elected a deputy to the Supreme Soviet.
In 1953 he became party head of the entire Leningrad district, and in 1957 was appointed to the presidium of the Communist Party.
Frol Kozlov's path to power was typical for party leaders of his generation of Soviet.
By 1963, when Kozlov was de facto second secretary of the Soviet Communist party, he seemed to Western Kremlinologists to be leading conservative resistance to Khrushchev's reforms.
Shortly after Khrushchev berated Kozlov for this mistake (but not necessarily because of Khrushchev's tirade), Kozlov suffered a stroke, which removed him from participation in the Presidium, although he formally remained a member until Khrushchev's ouster in October 1964.
He died shortly after his removal from office.
He was buried in the Kremlin Wall Necropolis.
Quotes from others about the person
“Anastas Mikoyan labeled him an "unintelligent, pro-Stalinist reactionary and careerist. "”