Hopkinton State Park has two beaches and they are not interchangeable. The Massachusetts Department of Conservation and Recreation lists them as Hopkinton Main Beach and Upper Reservoir Beach. The Main Beach, also called the Lower Beach, sits below the park's historic earthen dam on a separate bathing pond. The Upper Beach is the one on Hopkinton Reservoir itself, above the dam, and that is the larger body of water where all the park's boating happens. If you are looking at pictures of small sailboats and kayaks on open water with a wooded island in the middle, you are looking at the Upper Beach's reservoir.

The difference matters most for lifeguards. In DCR's 2026 waterfront services schedule, Hopkinton Main Beach gets weekend coverage early in the season and seven day coverage from mid June onward, while Upper Reservoir Beach is listed as unguarded for the entire season. Both are designated swimming areas, so both get restrooms, parking and routine water quality testing, but nobody is watching the water at the Upper Beach. The swimming season runs late May through Labor Day. Where guards are posted, swimming stops at 5:45 PM. The park gates are open 8:00 AM to 6:30 PM.

Parking is metered and fees are charged from Memorial Day weekend through the Monday of Columbus Day weekend. The rate is set by your license plate: 8 dollars for a Massachusetts plate, 30 dollars for an out of state plate. The meters take no cash. You pay at the lot or through the YODEL app and leave the pass on your dashboard. Massachusetts residents can buy an annual DCR parking pass for 60 dollars, and residents 62 and older can buy a lifetime senior pass for 10 dollars, though that one is not sold on site. Parking is free for vehicles with a disability plate or placard, a Purple Heart plate, or a disabled veteran plate. DCR closes the park temporarily once the lots reach capacity, which happens on hot summer weekends, so arriving early is the whole game.

The hazard specific to this beach is bacteria. The Upper Beach has been closed on its own while the Main Beach stayed open, after enterococci counts came back above the state freshwater limit of 61 MPN per 100 mL. Hopkinton's health director attributed it largely to the resident goose population, along with pets and swimmers, and pointed out that the water in this part of the reservoir does not move through the way it does in a flowing pond. DCR tests daily during a closure to decide when the water is safe again. Check the state's Interactive Beach Water Quality Dashboard before you make the drive.

Facilities include restrooms, a boathouse, a car top boat ramp, hundreds of picnic tables with charcoal grills, two reservable pavilions, an accessible beach and beach wheelchairs. Regatta Point Community Sailing runs the seasonal rentals on the reservoir for kayaks, paddleboards and small sailboats. No motorized watercraft anywhere in the park. Flotation devices are not allowed in the swimming areas, but Coast Guard approved life jackets always are. Dogs have to be leashed and are banned from both beaches from May 1 through September 15. Grilling is confined to the designated picnic areas, and groups over 25 need a special use permit.

The reservoir was built between 1891 and 1894 to impound part of the Sudbury River watershed for Boston, and the 650 foot granite stepped spillway at its east end is on the National Register of Historic Places. Once the water came out of service for drinking, the state opened the park in 1947. More than 10 miles of trails run through the roughly 1,500 acres around the water. The park entrance is at 164 Cedar Street in Hopkinton.