The father of the German tenor, Leopold Clam, was a contrabass player in the orchestra of the Königlichen Oper Berlin (Royal Opera Berlin). His training as the singer took place in Berlin, but a first engagement in 1939 was prevented due to his drafting as a soldier in World War II. So he could begin his career as a concert singer in Berlin only in 1946. He became member of the RIAS-Rundfunk-Chor.
In 1948 Leopold Clam received engagement at the Städtischen Oper Berlin, the later Deutschen Oper, to which he belonged for more than forty years until 1988. At this opera house he took part in a set of opera premieres, such as in 1951 in Amphitryon by R. Oboussier (as Sosias), in 1952 in Ein Preußisches Märchen by Boris Blacher, in 1958 in Fiesta by D. Milhaud, in 1960 in Rosamunde Floris, also by Boris Blacher. At the Schwetzinger Festival he sang in 1971 in the premiere of the opera Melusine by A. Reimann, and in 1956 in H.W. Henze's König Hirsch, as well as in the German first performance of Luigi Dallapiccola's Volo di notte ('Night Flight'), which likewise took place in 1956.
Leopold Clam's stage repertoire included above all smaller and character roles, as Antonio in Figaros Hochzeit, Kilian in Freischütz, Ulrich Eisslinger in Meistersingern, Mesner in Tosca, Benoît in La Bohème, Matteo in Fra Diavolo by Auber, Dancairo in Carmen, Arzt in Pelléas et Mélisande by Debussy, Yamadori in Madame Butterfly, which are only few roles from his very comprehensive repertoire. In November 1988 he appeared for the last time on the stage of the Deutschen Oper Berlin, at which he had appeared in about 4,000 performances, as Wird in Rosenkavalier by R. Strauss.
Numerous recordings, particularly on HMV (smaller roles in complete operas, as Meistersinger, Carmen, Hoffmanns Erzählungen), on DGG (Lulu by Alban Berg), Urania (Wiener Blut by J. Strauss), Columbia (selection from La Bohème), Opera (also selection from La Bohème).