The Saints signed Johnson on Wednesday, the New Orleans Times-Picayune reports.
Johnson has jumped between the Saints' 53-man roster and practice squad over the past three seasons, but in 17 appearances between 2014 and 2015, he totaled 12 carries for 31 yards and seven receptions (on 10 targets) for 45 yards. At the outset of the offseason, he'll be measuring himself against fellow fullback Toben Opurum.