Born in southern Bavaria, he studied philosophy and theology in Munich. On hearing about the work of the Redemptorists among German-speaking Catholics in the United States, he came to this country in 1843. Ordained at the end of 1844, he was assigned for six years to St. Philomenas Parish in Pittsburgh as an assistant to St. John Neumann [whose feast is observed on January 5]. The next three years Father Seelos was superior in the same community and began his service as novice master.
Several years in parish ministry in Maryland followed, along with responsibility for training Redemptorist students. During the Civil War, he went to Washington, D.C., and appealed to President Lincoln that those students not be drafted for military service.
For several years he preached in English and in German throughout the Midwest and in the Middle Atlantic states. Assigned to St. Mary of the Assumption Church community in New Orleans, he served his Redemptorist confreres and parishioners with great zeal. In 1867 he died of yellow fever, having contracted that disease while visiting the sick. He was beatified in 2000.