Central midfielder McGeehan, 24, lengthened his deal, which was due to expire next summer, until 2021 after starring in the promotion campaign.
He joins winger Jacob Brown and striker Cauley Woodrow in signing new deals this summer, after central midfielder Alex Mowatt did the same during the promotion campaign.
The Reds are also understood to be interested in tying down winger Mamadou Thiam and centre-back Ethan Pinnock to longer deals, as they both have one year remaining on their current contracts. Negotiations have taken place with the representatives of both players.
Thiam, the 24-year-old Frenchman, played in every league game during the promotion campaign and scored seven goals while the Reds are understood to have rejected two bids for him in January.
Pinnock, 26, started every league match last season and was voted Player of the Year by the fans while also being named in the League One Team of the Year.
The Reds would also like to extend the contract of head coach Daniel Stendel, who is midway through the two-year deal he signed when he arrived last summer. But Stendel is thought to be waiting to see what transfer business is done in the summer window before deciding whether to commit his future to the club he led out of League One in his first season of English football.
Meanwhile, McGeehan says there were ‘other options out there’ for him this summer but is glad that he is the latest of Barnsley’s promotion heroes to extend their deal. He told the club’s website: “We’ve got a good young group of players. “I’ve joined a couple of others in being in the first group to sign new contracts so that shows the belief we have in the club and the loyalty we have to the fans.
“It’s so important to do it early. That shows that we have a great young group of players and we have a great chance of growing together. We all want to stick with each other and be here. “We’ve got a good young manager as well (Daniel Stendel), he’s brought our games on a lot and we need to keep learning while getting loads of games together in the Championship. There were some other options out there, but I was always focused on Barnsley, I think that’s the right attitude.”