City are odds-on favourites to claim the trophy at Wembley tomorrow, with Wigan's preparations having been overshadowed by their relegation battle.
Yet, despite the Latics being in deep trouble at the bottom of the Premier League, Kompany rates them highly.
Wigan outplayed City for large spells of their meeting at the Etihad Stadium last month – only to lose to a late Carlos Tevez goal – and Kompany thinks they have been one of the season's toughest opponents.
That is some compliment from the skipper of a side that has faced two Champions League semi-finalists in Borussia Dortmund and Real Madrid this term.
Kompany said: "They are one of the more difficult sides we have played this season. You can see it's a team that doesn't fear keeping possession.
"When it's going well for them they are a very difficult team to play against. We have to be careful.
"When they played at Etihad, they were really good and caused us a lot of trouble.
"But we managed it really well in the end. We didn't concede and we won.
"I think they are a good team and if people think they will be easy then it is a mistake."
City rested several players for their midweek win over West Brom in preparation for the final.
Kompany, Yaya Toure, Pablo Zabaleta and Gael Clichy were given the night off while Sergio Aguero and David Silva did not get off the bench.
There was some concern about Toure, with the influential midfielder also withdrawn at half-time of last week's game at Swansea through fatigue, but he has declared himself fit.
The 29-year-old, who scored the winner against Stoke in the 2011 final, said: "I am good. Sometimes it is difficult to play all the games at the same level and sometimes you can get an injury.
"But we have worked on that, trying to keep injury far away and concentrate on delivering at the weekend.
"I am already fit. I started training three days ago and I am well in now.
"I want to deliver a good game and help the team to achieve something important."
Winger Scott Sinclair is out after undergoing surgery to remove a blood clot in shoulder, but otherwise City have no major injury concerns.
Back-up goalkeeper Costel Pantilimon is expected to be selected ahead of England number one Joe Hart, having played in all the previous rounds.
Meanwhile, City striker Edin Dzeko has suggested he could be playing elsewhere next season.
Dzeko, who has scored 14 goals this season, has been the subject of transfer speculation as City consider a summer revamp of their squad.
When asked if he could leave, he said: "We will see. Everything is open."
Dzeko earned a tag of 'super sub' earlier this season after a spell of scoring goals off the bench. Six of his first seven came as a substitute.