Holbrook is a town in Norfolk County, Massachusetts, United States. As of 2023, the town's population was 12,284. Holbrook was first settled by Europeans in 1710 as the southern part of Old Braintree, and was officially incorporated on February 29, 1872, the last town created from the former lands of Braintree. It used to be known as East Randolph, being divid…Holbrook is a town in Norfolk County, Massachusetts, United States. As of 2023, the town's population was 12,284. Holbrook was first settled by Europeans in 1710 as the southern part of Old Braintree, and was officially incorporated on February 29, 1872, the last town created from the former lands of Braintree. It used to be known as East Randolph, being divided from Randolph by track from the Old Colony Railroad line.