St Johns College was established in 1969 as Dubbo's Catholic co-educational high school for students in Years 7 to 10. This was the result of the amalgamation of the De La Salle Boys College (1936) and St Patrick's College for Girls (1880s).
The College accepted its first Senior Students into Year 11 in 1986. The first HSC graduating group was the class of 1987.
The College is located at Sheraton Road in a rural environment set on 40 hectares. College enrolment is approximately 990 students. There are 82 teachers as well as a variety of support and ancillary staff. Two School Counsellors are also available for students and families.
St Johns College is the only Catholic Systemic Years 7 to 12 school to service the immense Western Region between Orange and the borders of New South Wales with South Australia and Western Queensland. The College provides a secondary Catholic education for Dubbo and the neighbouring towns. Boarding facilities are available in Dubbo, but are not provided by the College.