In 1995, Frolov became a student at the director's faculty of RATI. After graduating, the actor was invited to work with the Lenkom troupe, and he agreed. Frolov made his debut on this stage when he participated in the production of "Cruel Games." In this play, Sergey played Terenty, for which he was awarded the "Moscow Debuts" theater festival prize in 2000. The actor won in the category "Best Male Role."
However, the most significant event for the actor was the play that brought Sergey success and fame. It was a production called "Balakirev the Jester," in which he played the lead role. It was for his excellent performance as Balakirev the Jester that Sergey Frolov became a laureate of the "Crystal Turandot" award. In 2003, the actor became a laureate of the State Prize of the Russian Federation.
Sergey Frolov also worked at the "Quartet I" theater, where in 2010 he participated in the production of "Duck Hunting." Then the actor starred in a six-episode project called "Lucky You" alongside Beroev, Kostolevsky, and Chursin. The movie was directed by Plotkin.
In November 2011, the premiere of the movie "Kaby," directed by Oleg Osipov, was scheduled. The filming took place in Vietnam. Sergey Frolov has also been participating for several years in the play "The Master and Margarita," which is staged at the K. S. Stanislavsky Theater. There, the actor is involved in several roles, playing Berlioz, Poplavsky, and Bengalsky. He performs with Lyudmila Gurchenko in the play "The Accidental Happiness of Policeman Peshkin."