Leopold Wallner was the son of a of Polish mother and Austrian father who was a music publisher in Kiev. In 1866 the family moved to Brussels. In 1866 he shortly studied harmony and composition with Fetis and Henry van Synghel at the Brussels Conservatory. In 1867 when his father died he had to stop his study and make his living by teaching, but later in life he lectured at the conservatories of Brussels and Ghent and the music schools of Schaerbeek, Louvain and Mons.