Some years later Suhr went back to Denmark, where he became increasingly preoccupied with life's basic questions.

During a visit to Rome in 1925, Suhr was intrigued by Catholicism, and on 17 January 1926 he converted to the Roman Catholic Church.

Suhr became bishop and took place in San Girolamo on 15 January 1939 when St. Ansgar's Cathedral in Copenhagen was inaugurated on 3 February 1939.

In the 1960s, Suhr was a member of the Second Vatican Council's preparatory commission as head in Rome.

Bishop Johannes Theodor Suhr died on 10 March 1997, aged 101 in Aabenraa.