In 1954, the Most Reverend Bishop Lawrence H. Sheehan and the Diocese of Bridgeport purchased a twenty-six acre site on Newfield Avenue in Stamford that would become Stamford Catholic High School (“SCHS”).  On September 3, 1958, SCHS opened its doors to freshmen, sophomores and juniors as a Roman Catholic, coeducational, college preparatory school under the direction of the Diocese of Bridgeport.  The school was incorporated in 1963.

Following the closings of two diocesan high schools, Central Catholic in Norwalk in 1990, and St. Mary in Greenwich in 1991, Stamford Catholic High School was re-named Trinity Catholic High School (“TCHS”) as part of a merger of the three schools.

Today, TCHS continues its longstanding tradition of rigorous academics, outstanding athletics and community service excellence while modernizing infrastructure and facilities to be in line with today's advances in technology.

As of June, 2018, the school has begun work on Bishop Frank Caggiano's "Imagine 2020" Campaign.  Phase One and Two will be to install two new labs, re-work the Guidance wing, and add a Media Center, offices and classrooms on the third floor.  Phase Three will be building out the lower level of the school to acccomodate The Catholic Academy of Stamford's 6th, 7th and 8th graders move to the campus in late Spring 2019. Once that move is complete, work will begin on the old middle school building to  house the PreK through 5th grade students by end of school year 2020.