After finishing school in 1949 he enrolled in the Geological research faculty of the Moscow's Gold and Non-ferrous metals Institute where he studied up until 1955, making frequent trips to the Central Asian Soviet republics for professional practice.

Back in Moscow, Belyavsky continued working as a geology engineer, occasionally taking part in amateur theatrical productions staged by The Teachers' House.

In 1964, he left the Satire Theatre but never severed ties with its troupe, having become the co-director (with Georgy Zelinsky) and the first presenter of the popular TV series Pub "13 Chairs".

All in all he appeared in more than one hundred films (working in Poland, East Germany, North Korea, Finland, France, Chekhoslovakia, United States), one of his best-known roles being that of villainous Fox in Stanislav Govorukhin's The Meeting Place Cannot Be Changed (1979).

[7] After Boris's death they have adopted another son, who committed suicide after being told by neighbors that Alexandr and Lyudmila are not his biological parents.