Jamie Donaldson and Gary Murphy each carded rounds of 3-under 67 on Saturday to share third place at 9-under-par 201.
Hansen did nothing on the front nine but collect his second bogey in three rounds at the par-4 fourth hole. It was his play on the back nine that sent the Denmark native to the top of the leaderboard.
He birdied the 10th and 12th holes to get within two shots of Lafeber, who was already in the clubhouse at 10 under par. Hansen drained a 25-footer for birdie at the 14th and added another long birdie putt at the next hole to match Lafeber in first.
Hansen used an iron off the tee at the short par-4 17th and knocked his approach to inches. He tapped in for birdie and went to the par-5 closing hole at Hilversumsche Golf Club with a chance at a two-shot lead and a 29 on the back side.
At the 18th, Hansen found the fairway off the tee and had a good chance of reaching the green with his second. That approach sailed right and found a greenside bunker. Hansen had very little green to work with and blasted out to 10 feet. The putt was never on line and instead Hansen settled for a one-shot lead.
'The putts were dropping on the back nine and they weren't on the front nine, and that was the difference really,' said Hansen. 'Today, driving was so easy for me. If you do that around here on this course, you're doing fine.'
Hansen broke through with his first victory at last year's Irish Open and it looked like bigger things were ahead. But in 2003, Hansen has only collected two top-10s, but is in a good position for his first trip to the winner's circle this year.
'It has been a strange year as I have put myself in contention a lot of times and then dropped back,' admitted Hansen. 'It has been painful sometimes but you learn from your mistakes and I am a little closer to where I was last year in the summer. My game is slowly turning around and the second win will be lovely. If it doesn't happen tomorrow I am sure it will in the future.'
Lafeber had the opposite round of Hansen on Saturday as he flew out of the gate with back-to-back birdies at one and two. He added four birdies in a five-hole span from the sixth but fell from there.
Lafeber squandered chances for birdie at the par-5 12th and a short putt at the 15th. He did not take advantage of the par-5 closing hole but matched the lowest round of the tournament with a 6-under 64.
'I parred the last eight holes but I hoped to pick one or two shots, especially on the 12th and 18th,' said Lafeber, who has a chance to become the first home winner of the Dutch Open since Joop Ruhl in 1947.
Lafeber is still in search of his first win on the European Tour and where better than his home country.
'It would be huge to win tomorrow especially as it would be my first win and as a pro you want to win your home tournament,' said Lafeber. 'But it will be a long day tomorrow and there are a lot of guys behind me so it will be an interesting day. What I wanted today was to give myself a chance for tomorrow, which I have done.'
Fredrik Andersson eagled the last hole to shoot a 1-under 69 and is tied for fifth with Steen Tinning (69), Nicolas Colsaerts (66) and David Park (67) at minus-8.
Fredrik Widmark, the overnight leader, was 7 over par after his first 11 holes but collected two birdies on the way into the clubhouse. He shot a 5-over 75 and is part of a group tied for 25th place at 4-under-par 206.