Spencer Brook is an unincorporated community in Spencer Brook Township, Isanti County, Minnesota, United States. Isanti County Roads 7 and 40 are two of the main routes in the community.
Spencer Brook is located between Bradford and Princeton. The Rum River and Spencer Brook both flow through the community. Spencer Brook was one of the first communities in Isanti County, settled in the late 1850s by Yankees from the east coast, many Civil War veterans. Spencer Brook includes the historic country school and the Spencer Brook United Methodist Church.
It was named after Benjamin Nicholson Spencer (1806-1881) who came from Turkeyfoot, PA and came to Minnesota in 1854 and was Alderman of the 1st Ward of Spencer Brook Township. Benjamin was a Judge, carpenter, and farmer.