A hamstring problem caused Costa to miss Sunday's 1-1 home draw against Malaga, a result that sent the title race in Spain to the wire.
Atletico could have sealed their first Liga crown since 1996 with victory but now have to avoid defeat at Camp Nou to achieve the feat, with second-placed Barca still harbouring title ambitions of their own.
Costa's involvement was in doubt but Simeone revealed on Friday that the striker – who has bagged 36 goals in 50 appearances in all competitions this season – would play.
"Diego Costa is alright. He trained normally without any problems. He will start against Barcelona," Simeone said.
Simeone is under no illusions as to the size of the task confronting his side, particularly in the Catalan cauldron.
He has predicted a fast start from Gerardo Martino's men but feels his side are prepared for whatever gets thrown at them.
"I expect Barca to come out strong and am anticipating it to be the hardest of our recent matches against them," he added.
"They have an extraordinary team and play at home. It will be one of the most complicated Barcelona teams we could possibly deal with.
"I believe that Barcelona are always a dangerous team irrespective of their tactical plans and which players they field. They have several variants and are a team that's used to attacking.
"All we can do is give our all and put in a great game.
"But we know what to expect. We know where our strengths lie and what our weaknesses are. We have to put in a great performance."
Atletico have the small matter of a UEFA Champions League final next week and increasing the importance of the Lisbon showpiece is the fact it comes against cross-city rivals Real Madrid.
But Simeone has stressed that the derby showdown is not on Atletico's radar for the minute.
"No one is thinking about the Champions League final right now," he continued.
"There is a lot of nice build-up to come, but we're focused on tomorrow. We live in the moment.
"There is no need to motivate the players ahead of a big match like this. The coach's job is to get the team prepared and we are trying to come up with the best ways to make sure the match is played on our terms.
"Here's hoping the team can deliver on the pitch."
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