Simpson was one of USA captain Tom Watson's wildcard picks for the illustrious team event at Gleneagles, starting September 26.
Sitting 19th in the FedEx Cup standings after two play-off tournaments, Simpson - who finished tied for ninth on Monday at the Deutsche Bank Championship - said a short discussion with Watson preceded him getting the nod.
"It was obviously one of the greatest calls I've ever had," the 2012 US Open champion said.
"There's a lot going on over the past few weeks with the Ryder Cup and me.
"So many guys that were playing well, that were going to be possibilities for picks. So, I knew I was in the mix but I had to play well.
"Last week was an emotional roller coaster for me and I didn't really know where I stood when I finished the golf tournament.
"I didn't sleep much last night. I got a call early this morning. Fortunately I was up.
"I saw 'Captain Watson' was calling me and he asked me a question about what he thought I brought to the team.
"We had a good conversation and he told me I was a pick. I was elated.
"It was five in the morning my time here but I got out of bed.
"Unfortunately I didn't have anyone to celebrate it with. I was by myself and I was pretty pumped up about it."
Simpson is on the US Ryder Cup team for the second time, after debuting in 2012 at Medinah.
The Barclays champion Hunter Mahan was another wildcard recipient, his recent win catapulting him to third in the FedEx Cup and virtually sealing his spot for the trip to Scotland.
Mahan, 32, was a part of the winning 2008 Ryder Cup team, before selected again for the Americans' concession of the cup in 2010.
The Texas resident said his form had been developing over a few weeks, before he broke through for his sixth career PGA Tour title.
"Obviously [The Barclays] was a huge, timely win. The game was coming around from the British [Open] on," Mahan said.
"I played well at Bridgestone, I played well at the PGA [Championship]. I felt things were right there.
"For some reason coming into Ridgewood, I had this calm over me and this great confidence.
"I felt fantastic about my game, I felt rested and went there and played well. Obviously that was massive for my FedEx Cup and making the Ryder Cup team.
"If I hadn't have won there I would have had to have played extremely well last week to be a part of this team so, winning is everything in golf.
"I couldn't have won a bigger tournament at the right time."