- Cambridge Savings Bank 1834-present
- Schoenhof's 1856-present (since 1940 in Harvard Square)
- Harvard Coop 1882-present
- Leavitt & Peirce 1883-present
- Cambridge Trust 1890-present
- J. August 1891-present
- LaFlamme Barber Shop 1898-present
- Brattle Square Florist c.1905-present
- Alice Darling Secretarial 1913–present
- Tennis & Squash Shop 1924-present
- The Grolier 1927-present
- J. Press 1930-present
- Bob Slate, 1930-present
- Harvard Book Store, 1932-present
- CCAE 1938-present
- Dickson Brothers, 1942-present
- The Swiss Watchmaker, c. 1940s-present
- Cardullo's 1950-present
- Charlie's Kitchen 1951-present
- Andover Shop 1952-present
- Brattle Theatre 1953-present
- Hong Kong 1954-present
- Out of Town News 1955-present
- Casablanca 1955-present
- Cafe Pamplona 1959-present
Many Harvard Square businesses become institutions by virtue of their longevity. Here are some that made it a half-century or longer.