Bernard Cossmann was born in 1822 in Dessau, Germany. His father was a merchant. He studied cello with Dreschler and Muller, and finally with Kummer at Dresden. In 1840, at the age of 18, he was appointed principal cellist at the Italian Theater in Paris. The same year he began concertizing, and made appearances in London, Berlin and Leipzig. Mendelssohn chose him to be solo cellist at the Gewandhaus Concerts in Leipzig. In 1849 he traveled and performed all over England and Ireland, and played for Queen Victoria at Windsor Castle. He became a friend of Franz Liszt, and played at the first performance of Wagner's Lohengrin at Weimar in August 1850, with Liszt conducting. He became solo cellist to the Duke of Weimar, and held the principal cellist position in the Weimar Orchestra for sixteen years.
Cossmann toured Russia in 1866, and became a professor at the Russian Imperial Conservatory, where he stayed for four years. After that he settled in Baden-Baden, and concertized with Brahms, von Bulow and other famous muscians of the time. In 1878 he became a professor at the Hockschule in Frankfurt, and held that post until his death in 1911.
Cossmann studied composition with Moritz Hauptmann in his youth, and did much composing and editing of works for cello. Not many of his compositions are in vogue today, except for his Etudes de Concert Opus 10, and his cello Etudes.