Jackson, 24, is 6-foot-5 and appeared in nine games with the Wizards last season as a rookie, after being signed to a two-way contract in February.
He first signed with Washington in September but was waived a month later, just before the start of the season. In the nine games Jackson did appear, he averaged 6.2 points.
Most of this time was spent with the Capital City Go-Go of the G League, where he averaged 15.5 points, 4.2 assists and 3.8 rebounds in 29 appearances.
Washington will have two two-way slots filled in Butler and forward Eugene Omoruyi. This marks the first season teams can carry three two-way players.