 While developing in the field of architecture, Catellanos continued his religious vocation, joining the convent of Franciscan friars in Aguascalientes, in 1938.Two years later he returned to Guadalajara, ordained a priest, and in the 1940s he headed the Diesis Commission on the Arts.He built a series of religious buildings around the state, including the Main Seminary, the chapel at Ciudad Granja, and the churches of Solitude, Holy Cross, and the Sacred Heart, as well as others in small towns.