The Argentina international is Inter's leading marksman in the league this term - only Juventus' Carlos Tevez has improved on his return of 14 goals.
There were fears that Icardi would be unable to make the trip to Stadio San Paolo due to a muscular injury.
However, head coach Mancini refuted those suggestions, saying: "Mauro Icardi is fine and he'll be involved.
"We might change one or two things but otherwise it will probably be much the same line-up."
The match against Napoli sees Inter go head-to-head with former coach Rafael Benitez.
Inter are looking to bounce back from a lacklustre 1-0 defeat to Fiorentina last weekend - a result that left them 10 points adrift of Napoli and the UEFA Champions League places.
However, Mancini is confident that he is developing a team that will be among the contenders for the title next term.
"The team has made a lot of progress," he added. "Next season we'll have a side capable of challenging for the title.
"We must make sure that the work we're doing at the moment - and we're giving our all - brings us results.
"The players are fairly calm, they can see they're getting better. We must never forget that we're Inter."
