Lillenas emigrated to America as a child. He attended Deets Pacific Bible College in Los Angeles, California (later renamed to Pasadena College); studied music at the Siegel-Myers School of Music in Chicago, Illinois; and received an honorary Doctor of Music degree from Olivet Nazarene College. In 1924, he founded the Lillenas Music Company (later taken over by the Nazarene Publishing Company), and worked as an editor there for 20 years.

Haldor married Bertha Mae Wilson, a songwriter like himself. He and Bertha were elders in the Church of the Nazarene. Haldor traveled as an evangelist, then pastored several churches, 1914-1924. In his lifetime, he wrote some 4,000 hymns, and supplied songs for many evangelists.