Located in the northwestern corner of the county, and of the state, along both the Indiana state line and the Michigan state line, it borders the following townships: No municipalities are located in Northwest Township.

The township lies within the Toledo Strip, a contested ribbon of land over which Ohio and Michigan came to blows in an 1835–36 confrontation known as the Toledo War.

[4] The unincorporated community of Nettle Lake, also a census-designated place, is in the northern part of the township, at the south end of the lake of the same name.

Northwest Township was organized in 1840, and named for the fact the extreme northwestern point of Ohio is located within its borders.

[6] The township is governed by a three-member board of trustees, who are elected in November of odd-numbered years to a four-year term beginning on the following January 1.