Playing together in the second-to-last pairing at The International on the outskirts of Amsterdam, Garcia and Shinkwin traded birdies all day.
Garcia drew level on the par-5 18th, just missing a tricky eagle putt over a slope on the undulating green before tapping in for birdie, while Shinkwin could manage only a par after finding a bunker behind the green with his second shot.
The Spaniard has made just one bogey in the first three rounds.
"That's always a nice thing to have on a week," Garcia said. "Enjoying that, and we'll try to do more of the same tomorrow."
Nicolai Hojgaard, an 18-year-old Dane, was alone in third place, two strokes back.