The Newmills runner broke the record at Belfast’s Victoria Park on Saturday, shaving one second off the previous 5km mark set by British Olympian Andy Butchart.
Griggs completed the 5km course in 13 minutes and 44 seconds.
The 19-year-old surpassed Andy Butchart’s 13.45 mark set in Edinburgh last June.
Speaking on BBC NI’s Good Morning Ulster, Griggs admitted he was pleased with the result.
“I wasn’t going into it trying to break the record,” he said.
“I was just doing it as a hard run out, as I have a race next week.
“I thought before I was in good shape and was within a chance of breaking the record. It was a good feeling.
“I don’t think anybody really knew until we finished and I looked at my watch and saw it was a second off the world record. It was pretty shocking. I wasn’t really thinking about it.”
Parkrun does not recognise times as world records or world bests, describing its events as a “run and not a race”.
Last year, fellow Irish international Ciara Mageean set the women’s world best at the same Belfast venue, clocking 15 minutes and 13 seconds.
Griggs, who was previously Head Boy at Cookstown High School, first gained attention in 2021, winning the European Under-20 3,000m title at 16.
He has since won more European Under-20 medals and represented Ireland in the 1500m at the European Championships in Rome.
Despite missing out on a spot in the Irish Olympic team, Griggs bounced back with personal bests in the 1500m, 3,000m, and 5,000m.
In July, he set an NI 3,000m record of 7.36.59 at the Diamond League in London, moving to fourth on the Irish all-time list.
He also broke the NI 5,000m record with 13.13.07 at the Morton Games and ran a new 1500m personal best of 3.35.04 at the British Milers Club meeting in Tooting.
