Dier shot a 68 over the Slieve Russel Resort to move to 10-under-par for the tournament, one shot better than Stephen Dodd (68) and two better than Robert Jan Derksen (68).
Playing in his first full year on the European Tour, success has not come easy thus far for Dier.
In 21 events, the 24-year-old native of Germany has missed the cut 12 times ' including his last six attempts ' and has been inside the top-30 on only a couple of occasions.
He did show good potential earlier in the season, however, when he finished in a tie for ninth at the Mercedes-Benz South African Open, and he expanded on that promise Friday, rattling in five birdies against just a single bogey for 68.
The round followed Thursdays flawless performance of 66, which tied his best score for the year.
'This is a new experience,' said a happy Dier following his round. 'I'm very much looking forward to it. I've taken the smallest tournament first. It's not like leading the British Open after two days, but we will see.'
In second is Dodd, a career journeyman, who leading up to this season, had only collected two top-10 finishes throughout the 90s on the European Tour.
He did finish third this year at the Madeira Island Open, however, and with the majority of the top players from the circuit overseas this week at the PGA Championship, he is looking to take advantage of the golden opportunity and obtain his playing privileges for next season.
'Getting the card is the aim every week,' said Dodd. 'Today I did things right, kept the ball in play, and 68 it was.'
Despite a two-hour delay in the morning because of fog, the entire field managed to finish their rounds. The cut fell at even-par 144 and included 86 players.
Full-field scores from the North West of Ireland Open