Ondrej Lenárd was born in 1942 and had his early training in Bratislava, where, at the age of 17, he entered the Academy of Music and Drama, to study under L’udovít Rajter. His graduation concert in 1964 was given with the Slovak Philharmonic Orchestra and during his two years of military service he conducted the Army Orchestral Ensemble, later renewing an earlier connection with the Slovak National Theatre Opera.

Lenárd’s work with the Slovak Radio Symphony Orchestra in Bratislava began in 1970 and in 1977 he was appointed principal conductor. At the same time he travelled widely abroad in Europe, the Americas, the Soviet Union and elsewhere as a guest conductor, and during his two years from 1984 to 1986, as general music director of the Slovak National Theatre Opera he recorded operas by Puccini, Gounod, Suchoň and Bellini for the Opus record label. For Naxos, Lenárd has recorded symphonies by Tchaikovsky and works by Glazunov, Johann Strauss II, Verdi and Rimsky-Korsakov.

In the 1991–92 season Lenárd took over the position of principal conductor of the Slovak Philharmonic and in the period 1995–2001 he became principal conductor and music director of the Slovak Philharmonic. He has been permanent guest conductor of the Japan Shinsei Symphony Orchestra in Tokyo since 1979, and from 1993 to 2001 became its principal guest condutor, principal conductor and honorary conductor/music advisor. Since 2001 Ondrej Lenárd has been honorary conductor of the Tokyo Philharmonic Orchestra. From 2011 to 2018 he was the principal conductor of the Prague Radio Symphony Orchestra.