The 26th Middlesex District consists of Ward 1 Precinct 3, Ward 2 Precincts 1, 2, 3A, Ward 3 Precincts 1, 2, 3, Ward 4 Precinct 1, Ward 5 Precincts 1, 3, Ward 6 Precincts 1, and 1A, all of the city of Cambridge, Ward 1 Precincts 1, 2, 3, 4, and Ward 2 Precinct 1A of the city of Somerville, in the county of Middlesex. It includes the following places:

• Cambridgeport
• East Somerville
• East Cambridge
• Boynton Yards and parts of the Union Square area near Target
• Inman Square
• Central Square
• The Port
• Wellington-Harrington
• some of mid-Cambridge
• Brickbottom and the Inner Belt area
• Assembly Row
• parts of the Kendall Square area