Captain Brian Howard, defenders Mustapha Dumbuya, Jon Harley and Lubomir Michalik, midfielder Lee Williamson and striker Luke Rodgers have all left Fratton Park at the end of their contracts.
Caretaker boss Guy Whittingham told the club website: "Some of these players might have been expecting it, but it wasn't nice news to deliver.
"We thank them for their efforts while they were here and wish them all the best for the future."
The club have also lost striker Paul Benson after he went back to Swindon at the end of his loan spell.
It means Whittingham now has a first-team squad of 13 players to work with ahead of Saturday's trip to Scunthorpe.
The future of troubled Pompey is no clearer after the latest court hearing to resolve the sale of Fratton Park, and subsequently the ownership of the club, was put back until the end of the month.
Portsmouth are in the League One relegation zone, have not won any of their last 14 matches and face a 10-point penalty if and when they come out of administration.