The ex-Tottenham centre-back, 34, who played 76 times for Pompey before leaving when his contract expired at the end of last season, has put pen to paper in time to be included in the squad for Tuesday night's visit of Leyton Orient.
"I'm delighted to be back at Pompey and to have the chance to help out Guy and this great club," the former Portugal international told Pompey's official website.
"I can't wait to get out on the pitch again and play in front of the fantastic supporters at Fratton Park."
Caretaker Pompey boss Guy Whittingham said: "Ric is a great character and the fans love him because of the way he has played for us over the past few years. I don't think there are too many players around who read the game as well as he does."
Meanwhile, Portsmouth have also confirmed that on-loan defender Carl Dickinson has been recalled by parent club Watford.
Portsmouth Supporters' Trust chairman Ashley Brown, meanwhile, admits a 10-point deduction would leave the club with an uphill battle to retain their place in League One.
The managerless south-coast side moved a step closer to exiting administration on Thursday when PKF - led by Trevor Birch - signed a conditional agreement to sell the club to PST.
Leaving administration would see Portsmouth, who are currently 19th in League One following a six-match losing streak, lose 10 points and plummet into the relegation zone.
Brown knows the task in hand, but he is confident the club can beat the drop, telling Press Association Sport: "The 10-point deduction is going to make life very tough for us.
"We will put a case in front of the Football League as to why we believe that shouldn't be applied. Having said that, we are also realistic and know it is something we will have to face.
"That will make survival very difficult. We have already had one decent run of form this season and we just have to find that again to put a few wins together. We have been in this position before, we have got out of relegation battles before and I'm sure we can do it again."