Jefferson Township is one of twelve townships in Jay County, Indiana, United States. As of the 2020 census, its population was 684 (down from 770 at 2010) and it contained 292 housing units.
Jefferson Township was organized in 1837.
According to the 2010 census, the township has a total area of , of which (or 99.91%) is land and (or 0.09%) is water. The streams of Bost Run, Como Run, Jeff Run, Jutte Run, New Mount Run and Vale Run run through this township.
The township contains seven cemeteries: Bost, Flesher, New Mount Pleasant, Powers, Stephens, Stratton and Wentz.