The Old Saybrook South Green is a rectangular greensward bounded by Pennywise Lane on the west and Main Street on the east. To the north it abuts the lawns of two residential properties. It is located within the Old Saybrook South Green National Register Historic District, a residential neighborhood that reflects the wealth of the ship-building industry that was responsible for its development during the 18th and 19th centuries. Across Main Street to the east of the green is the dominant feature of the neighborhood, the Congregational Church, built in the Greek Revival style. A 19th century general store, now used as a pharmacy, is located at the corner of Pennywise Lane and Main Street. It is thought to have been moved to the site from the Boston Post Road c. 1874. It is the only commercial building in the area.

The evenly graded green has a manicured appearance heightened by the narrow sidewalk that runs along the northern boundary, Main Street and the southern tip. Trees provide shade along Pennywise Lane and the northern portion of the green. Trees provide shade along Pennywise Lane and the northern portion of the green. There are no monuments. Only the town historical society marker and historic streetscape identify the open space as a historically significant site.

The green is the focal point of the historic residential neighborhood and valued for the open space it provides. The site that functions as a green in Old Saybrook is the area in front of the Main Street Elementary School next to the Town Hall (built as a theatre by the Saybrook Music and Drama Society) on Main Street. It became the "Town Green" or "Memorial Green" in the 1950s when the triangular green at the intersection of North Main and Route 1 was destroyed by road improvements. The war memorial on the old site was moved to the front of the school and the area gradually became the town green. Memorial Day Parades were rerouted to include it, the area was landscaped so the monuments became the focal point, and c. 1975 gazebo was added by the Rotary Club for concerts, weddings and torch light Christmas services.