Campbell finished with 67 at The K-Club, the same score as Massimo Scarpa, Henrik Bjornstad, Maarten Lafeber and Mikael Lundberg.
The group sits one shot ahead of five others, including Darren Clarke and last weeks winner Colin Montgomerie, while eight others are two shots back.
It was a good start and the first eight holes were pretty special, stated Campbell, who birdied Nos. 1, 2, 4, 5 and 8, and then rattled off 10 straight pars to finish his round.
I lipped out on the third from ten feet and again on the sixth and seventh so it could have been a really great start. But Im tied for the lead so I cant complain.
Neither could Scarpa, who had a similarly good start at last weeks Murphy's Irish Open, before ending in a tie for 20th at minus-seven.
Yet, while the 31-year-old Italian knocked off six birdies on Thursday, he gave a shot back at the par-4 15th, when he made bogey. He remains postive of his game and his chances this week though.
My putting stroke was really good today, even though I three-putted the last for a par-five, claimed Scarpa. That can happen sometime but I am playing good golf just now.
Likewise, Montgomerie is also playing some of his best golf in over a year.
That round was very important, claimed Montgomerie, who ran away with last weeks tournament at Fota Island. To come off any win is great but that is no good if you then throw in a couple of 74s and go home early from here. Thats no use ' you have to try and build on that and thats what Im trying to do this month.
While reining United States Open champion Retief Goosen was one of the eight tied for 11th following a 69, defending champion Lee Westwood did not get off to the start he might have liked. He shot a 71.
Full-field scores from the Smurfit European Open