The South Africa international missed last weekend's 2-0 win over Doncaster because his work permit had expired but he has now received a new one.
Mokoena might not reclaim his usual central-defensive spot after Greg Halford and Ricardo Rocha guided Pompey to a first clean sheet in 11 matches in his absence. However, he could step into the midfield as Aston Villa loanee Jonathan Hogg is suspended following his red card at the Keepmoat.
Winger David Cotterill will be added to the squad if the paperwork on his loan move from Swansea is completed in time. Striker Danny Webber is still out with a cruciate injury.