Clements, 32, earned the win in his 256th start in the series.
Clements took the lead after he made contact with Tifft in the final turn of the road course, causing both to spin. Both drivers recovered, but Clements was quicker, taking the white flag first in his No. 51 Chevrolet.
Michael Annett, who was running in third, was too far back to take the lead. He managed to finish second ahead of Tifft.
Clements is the fifth driver to qualify for the Xfinity playoffs.
“I don’t even know what to say, I’m just shocked,” Clements told NBC. “This is a car built in 2008. Everything we’ve got is old and used. I just can’t believe it. I’m just, is this real? … It’s a total team effort. I’m just so happy. It’s pretty neat to win at Road America. It’s one of my favorite road courses. I want to say sorry to Matt Tifft. I definitely didn’t mean to spin him out there. I got in hot there and he kind of came down and I was there. We collided.
“I’m just so shocked.”
Jeremy Clements Racing is an independent, family owned team that was started in 2010. His father, Tony Clements, is the owner.
“My gosh, it’s crazy,” Jeremy Clements said. “Our budget a year is a fraction of a big teams’. This is just a dream come true. I want to drive for a big team, but it hasn’t been the way it’s gone. I try to keep doing this, to keep my name out here getting as much experience as I can in case I do get the call. To any big team guys. Look at me. Let’s go.”
Tifft, 21, had led six laps before the accident. He was searching for his first Xfinity win and the first for Joe Gibbs Racing at Road America.
“Obviously, no matter what it’s tough,” Tifft told NBC. “I wish we could have raced it out till the last lap. We were struggling on old tires. I don’t know if he had fresher tires there. He had a lot of speed there at the end. … It’s tough to come that close. But we’ll keep knocking on the door, it’s all we can do.”
STAGE 1 WINNER: James Davison
STAGE 2 WINNER: Daniel Hemric
WHO HAD A GOOD DAY: Michael Annett finished second for his career-best finish in the Xfinity Series in 186 starts. His previous best was third in July 2012 at Daytona and at Dover in Sept. 2012. … Brendan Gaughan finished fifth for his second top five of the year … Casey Mears finished ninth in his first start at Road America … NBCSN analyst Parker Kligerman finished 10th.
WHO HAD A BAD DAY: Ryan Reed was involved in multiple accidents, going off course more than once and continuing on. He finished 35th … On the last lap of Stage 2, Ross Chastain turned Justin Marks, who collided with James Davison. Davison then made contact with and spun Austin Cindric when he came back on track in Turn 6. Davison’s day ended in the garage with a cracked radiator. He finished 37th … Daniel Hemric won Stage 2 but finished 15th after he was caught speeding during a Lap 28 pit stop.
NEXT: VFW Sport Clips Help A Hero 200 at Darlington Raceway at 3:30 p.m. ET on Sept. 2 on NBCSN.