Cech has not played since he was carried off on a stretcher against Inter Milan on February 24 with a calf injury, but he is fit once again and will come straight back into Carlo Ancelotti's starting line-up at the expense of Ross Turnbull, who has been deputising.
Full-back Ivanovic, though, is out with the knee injury that forced him off at half-time in the weekend 1-1 draw at Blackburn while Ashley Cole, Jose Bosingwa and Michael Essien all remain on the sidelines.
Following the Champions League exit against Inter and the disappointing draw with Blackburn, Ancelotti knows his side cannot afford another slip up at rock-bottom Pompey as they look to reignite their title challenge.
"It's the most difficult moment of the season, this is true," said Ancelotti ahead of the Fratton Park trip.
"It's more difficult now and we shouldn't be afraid to admit that. We're working hard to try and close this moment with a victory.
"Every team has had a difficult moment in the season. Now is a very important moment and we have to end it immediately."