The 31-year-old has joined the Spitfires on a deal until the end of the season.
Tubbs could be handed his Eastleigh debut in the National League game at Kidderminster on Tuesday.
Ex-Bournemouth striker Tubbs has scored five goals for League Two side Portsmouth this season but he has not featured for Pompey since October.
Eastleigh have confirmed the loan signing of Portsmouth striker Matt Tubbs.