The couple, identified as Nicola Salvatore, 56, and Isabella Rotondo, 55, were killed by several gunshots.
Salvatore had a criminal record related to drugs, and had recently dodged another assassination attempt.
Italian police believe the double homicide was linked to another murder in San Severo last October.
Bari anti-mafia police are currently investigating the murder in search for the assassins.
Puglia's mafia, the Sacra Corona Unita (United Holy Crown/SCU), is Italy's fourth and smallest mafia after Calabria's 'Ndrangheta, Sicily's Cosa Nostra and Campania's Camorra.
With ANSA