Sinclair's early history is entwined with that of the Dayton YMCA. In 1887, the YMCA offered evening classes in bookkeeping and mechanical drawing to just 55 men who met in two rooms of the YMCA building. The College grew quickly and was offering a broad curriculum and services including dormitories when the YMCA moved to a larger building at West Third and Ludlow streets in 1910.

The YMCA moved once again, in the fall of 1929, to another, larger building on Monument Avenue. The curriculum had now been organized into several disciplines including a school of Liberal Arts, the Dayton YMCA School of Commerce, the Dayton Law School, and the Dayton Technical School. The College even offered several 4-year degrees at this point in its history.

In 1948, the YMCA College became Sinclair College when it was renamed in honor of David A. Sinclair, Secretary of the Dayton YMCA from 1874- 1902 and founder of the educational program.
Although the College was still housed in the YMCA buildings, by 1959  it was independently operated and separately incorporated as a non- profit institution of higher learning under the laws of the State of Ohio. The State Board of Education authorized Sinclair to continue to conduct a junior college program and confer associate degrees in arts and sciences.

The Montgomery County Community College district was created by Montgomery County Commissioners in June, 1965, and one month later, they appointed a nine-member board of trustees. The official plan for the community college was approved by the Ohio Board of Regents in February, 1966, and one month later its charter was presented.
As Sinclair achieved independence, it had outgrown its facilities in the Monument Street building. Courses and faculty offices were scattered over an area of downtown Dayton that required some students to walk several blocks between classes.  Faculty members and counselors had no facilities for private meetings with students.  It was time for the College to move again.  Twenty acres of vacant urban renewal land downtown was acquired for the new campus.
Edward Durell Stone of New York, and Sullivan, Lecklider and Jay of Dayton were named architects for the new campus.  They envisioned and achieved a quiet oasis in the heart of the city with buildings that project strength and permanence, amazingly futuristic despite their thirty years of service to the community.

The original seven buildings of the new Sinclair campus opened their doors to students in September, 1972. Since that time the curriculum has grown to over 100 separate programs and the campus has grown to 19 buildings. Courses are also offered at many remote sites and online.

The voters of Montgomery County have always been Sinclair’s most valued supporters.  They showed their approval of a Community College District for Montgomery County in May of 1966, by passing a one-mill levy for 10 years, to support it. In 1975, the levy was renewed and, in 1989, voters again voiced their confidence in the college by passing a 2.5 mill, ten-year levy.

Sinclair's academic excellence has been acknowledged on an ongoing basis by accolades from accrediting and higher education governing bodies. In 1989, Sinclair was selected for membership in the prestigious League for Innovation in the Community College, and, in 2001, became one of the League’s elite Vanguard Colleges.  "Vanguard" is a term designated by the League to recognize the top twelve two-year institutions in North America that focus constantly on student and learner access and success.