While at the St. Joseph’s Institution,he accepted the Christian faith taught by the Catholic missionaries and became a Catholic. Soon after completing his schooling ,he took up the position of being a Catechist and worked three years in Francistown.He was at Our Lady of the Desert Catholic Church as the teacher of the faith of the people and the first assistant to the missionary priests.It was challenging times where transportation was not easy and it took time to get to one village to another. Going to Maun took three days if lucky to get a ride on a public vehicle. His normal mode of transport was a bicycle.

Hearing the call of God while at prayer to serve the church as a priest,he made the bold decision to enter the seminary to the chagrin of parents. With explanation and little persuasion from the young man,the parents gave in to his request and realesed him to follow his vocation. In 1957 he went to Chishawasha in the then Rhodesia ( Zimbabwe ) to study for priesthood. He spent seven years in formation.

On the 22 July 1963 he was ordained a Catholic priest in Francistown. After ordination Fr. Boniface returned to the seminary to do one more year of studies knownas the Pastoral year as was a norm at the time.Upon his return in 1964, he was appointed assistant parish priest of Our Lady of the Desert Parish in Francistown.Having worked for 8 years in Francistown, he was transferred to Gaborone and was appointed to the Christ The King Cathedral as the Administrator. In 1974, he was appointed a Monsignor by Pope Paul VI. He worked closely with the late Bishop Urban Muphy,CP of blessed memory. At the death of the first Bishop of Gaborone, Pope John Paul II appointed Fr. Boniface T. Setlalekgosi as the second Bishop of Gaborone. he was ordained on the 6th of March 1982 in the National Stadium.

Bishop Boniface is the second Motswana to be ordained a Catholic priest after Fr, Motsumi,OMI. He was the first priest to be ordained in Botswana. He was the second Bishop of Gaborone and the first Motswana to be appointed Bishop of the Catholic Church. Under his leadership the Catholic Church grew in leaps and bounds in the country. From a few parishes along the railway line,the church grew to all corners of the country. His love of pastoral work saw him in remote areas visitng the small pockets of Catholics scattered in the country. He was a shepard par excellence. He knew and visited most villages in the country.