St. Thomas College (STC), Thrissur was established in 1889 in less than two years after the formation of the Vicariate Apostolic of Trichur was raised to the rank of Second Grade College in 1919 was the earliest First Grade College in the erstwhile princely state of Cochin in 1925 and is at present one of the largest and most reputed of the Arts and Science Colleges in Kerala.

Since 2002 the portals of this college were open to women as well. At present, St. Thomas' College is one of the largest and most reputed Arts and Science Colleges in Kerala.

At the national level, St. Thomas' College has been accredited with a B++ grade in 2004 by the National Assessment and Accreditation Council, an autonomous organization instituted by the University Grants Commission.

The college completed the re-accreditation process in September 2010 and NAAC accredited the college with a grade and 3.58 points out of 4.00.

With this grade the college stands first in district and III in state.