The Belgian birdied his last three holes in an eight under par 62 at Hilversumsche Golf Club to sit two shots ahead of England's Kenneth Ferrie and India's Shiv Kapur.
"That is the is best round I have had on Tour actually," he said. "I shot 62 once before - in Jakarta a few years ago - but today felt like the lowest scor of my career."
Challenge Tour graduate Colsaerts, the longest driver on The European Tour this season, reached the turn in 33 but burst to life with a back-nine 29 with birdies at the 11th, 13th and 14th before his closing hattrick.
"It's like a home tournament for me and I grew up playing very similar courses in Belgium so I feel very comfortable here in this course with the trees everywhere and a very traditional layout," said the 27 year old.
"There have been some changes here and they have done them very well. I love these courses because I am so used to the layouts."
Colsaerts is yet to win a European Tour title, but believes his game is getting close to where it needs to be.
"This is my first year back on Tour for three years and it has been very good for me to be able to come back out and feel comfortable straight away and start to get some good results," he said.
"I am realising again that I can compete at the highest level. I am still not happy with the level of my chipping and putting but I am always working on that."
Colsaerts was in the same group as former European Open winner Ferrie, who is currently 110th on The Race to Dubai and aware that a good performance this week could ease the anxiety surrounding his playing card for next season, with only the top 115 retaining playing privileges.
A closing eagle on the par five last certainly helped his cause, having been preceded by five birdies and a bogey.
Kapur - at 105th also precariously placed in The Race to Dubai standings - also eagled the 18th, his tenth, and from then on added four further birdies.
“I actually got off to a very slow start today,” said Kapur. “I bogeyed the first and was one over after eight holes but then I had a nice birdie on the 17th and hit a great approach to the 18th to two feet for an eagle and that really kick started my round.
“I don’t know what it is but I seem to score better when I bogey the first hole. It’s strange but maybe it just focuses me more or something I don’t know but I do seem to give myself a kick up the back side when I bogey the first.
“I am very happy with the start but I have to follow it up for the next three rounds. There have been encouraging signs recently but I have to do it over four rounds.”
Ryder Cup debutant Ross Fisher was part of a seven-way tie for fourth on five under, along with fellow Englishman Nick Dougherty, Argentine Tano Goya, France's Raphaël Jacquelin, Scot Richie Ramsay, Portugal's José-Filipe Lima and home favourite Joost Luiten.
Luiten, second in this event three years ago and once again looking the most likely of the Dutch contingent to challenge, said: ”It’s always good to start a tournament in your own country with a good round so I am very pleased with the day today.
“I didn’t have any bogeys on the card today and that always helps your score. My putting was very good as well today and that really took the pressure off my ball striking.”
US PGA Championship winner Martin Kaymer returned to action with a three under 67, while defending champion Simon Dyson enjoyed an unusual round - the Englishman did not deviate from par on a single hole in his opening 70.
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