Koussevitzky studied the double bass in Moscow, becoming a virtuoso, and in Russia, Germany, and England gave recitals at which he played his own compositions; his double bass concerto (1905) became a repertory piece. He first conducted in 1908 in Berlin and left the following year to form his own orchestra in Moscow and to found a publishing firm for Russian music; its catalog included works by Aleksandr Scriabin (Scriabin, Aleksandr) (whose music Koussevitzky especially championed), Sergey Rachmaninoff, Igor Stravinsky, and Sergey Prokofiev. After the Russian Revolution of 1917, he directed the State Symphony Orchestra in Petrograd (St. Petersburg), but in 1920 he left Russia. In Paris (1921) he organized annual concerts, conducting many new works by Russian and French composers.

From 1924 to 1949 in the United States, Koussevitzky conducted the Boston Symphony Orchestra and gave first performances of works by Aaron Copland, Roy Harris, Walter Piston, and other contemporary American composers. In 1931, for the orchestra's 50th anniversary, he commissioned works by Maurice Ravel, Prokofiev, and George Gershwin, as well as Stravinsky's Symphony of Psalms. He later assumed direction of the Berkshire Music Festival and in 1940 established the Berkshire Music Center, at which summer courses were given by outstanding American and European musicians. In 1942 he organized the Koussevitzky Foundation to commission and perform new works.

Koussevitzky's conducting style was highly individual. His interpretations of the works of Pyotr Ilyich Tchaikovsky, Jean Sibelius, and other Romantic composers were marked by rhapsodic animation, and he imparted a similar quality to compositions of the modern school.