The Department of Biological Sciences of the University of Santo Tomas started as the Department of Zoology of the former College of Liberal Arts. It provided the basic requirements for Biology in the Bachelor of Arts program as well as the Associate in Arts program, a two-year requisite in Pre-Law and Pre-Medicine. The existing interest in the objectives of the department led to the development of the B.S. Zoology program. Six graduates received the B.S. from 1936 to 1948. The first batch of post-war Majors in Zoology was granted their degrees in 1949. 

The department continuously stirred great interest in this field of study as proven by the consistently increasing enrollment in the years that followed. The pre-medicine program was strengthened in Chemistry, Mathematics, Physics, and Animal Sciences. This led to the development of the four-year B.S. General Curriculum. It was in the late 1970’s that the Ministry of Education, Culture, and Sports issued a directive that the B.S. General program be further infused with more dynamic sciences such as Ecology and Biostatistics. This eventually led to the evolution of the B.S. Biology program in the late 1980’s, hence, transforming the Department of Zoology into the Department of Biological Sciences. Now, the department is the largest in the College of Science in terms of student and faculty population. It is also a university-wide service department for Science, Technology and Society course and other related general education courses. 

Since its inception, the Department has been a witness to many changes and milestones. In 1979, the Department was the first in the Philippines to offer a B.S. Microbiology program making UST the only Philippine university offering the said degree. The department was likewise granted the status “Center of Development” (2006) and “Center of Excellence” (2010) in Biology by the Commission on Higher Education. The department boasts of having the greatest number of PhD holders among the four departments in the college. Its Biology program has been certified by the ASEAN Universities Network Quality Assurance (AUN-QA) in 2017.