VERSAILLES, 3 July 2015 (AFP) - The 25-year-old French number one carded a one under 69, the highlight of which was a 107-yard approach shot which brought him an eagle two at the sixth.
He stood at four under at the halfway stage, level with Spain's Rafa Cabrera-Bello, who came in earlier with a 70 and former world number one and French Open champion in 2009, Martin Kaymer of Germany who had a 69.
Five players were grouped a shot further back on three under - Englishmen Tyrrell Hatton (68), Daniel Brooks (66) and James Morrison (68), Jaco van Zyl of South Africa (71) and Francesco Molinari of Italy (69).
Dubuisson, aiming to become the first home winner at the French Open since Thomas Levet in 2011, had two birdies to go with his eagle.
But three bogeys, the last coming at the 17th when he missed a five-footer for par, cost him the outright lead.
"Played very well. I had two shots that I hit very good, 8 and 9, and finished in a bad spot. So I had two bogeys there," he said.
"But you know, on this course, when you start to make one bogey, two bogey, then you think that it can turn really bad.
"But I had a great round and I'm very happy about the way I played today. It was really tough out there with the wind this afternoon."
Cabrera-Bello, whose last win was in the 2012 Dubai Desert Classic, said that his form has been improving this year, but for some poor final rounds.
"Obviously some things had been going wrong because my scoring during the first two days, or even Saturday, as well, compared to Sunday is not quite the same," he said.
"But I'm working on that, so I'm going to keep knocking on the door and one day, it will open for sure."
Earlier in the day Graeme McDowell's hopes of pulling off a rare hat-trick of title wins at the French Open bit the dust.
The Northern Irishman, who has been struggling for form all year, added a second round of 78 to go with his opening 72 and at eight over par he was well outside the cut mark.
In an uncustomarily scrappy round, on one of his favourite courses, McDowell had three bogeys and two double-bogeys.
He had been bidding to become just the second golfer to win three straight French Open titles after Marcel Dallemagne in 1938, one year before the outbreak of World War II.
He also would have been just the sixth golfer to have landed a hat-trick of European Tour titles in the same event alongside Ian Woosnam, Nick Faldo, Colin Montgomerie, Tiger Woods and Ernie Els.
McDowell said he blamed his current slump on tinkering too much with his swing and technique.
"I've just got to strip it out, back to basics. I've got a lot of golf to play. Just need courage in my pocket, get out there and work it out," said the 2010 US Open champion.
"I know it's in there. There's a little bit of clutter in there right now, but that's golf. You take the rough with the smooth. It's been a great three or four years. I'll dig this out and I'll be back."
Also packing his bags for home was former world number one Lee Westwood of England.
An opening round of 73 was followed by an extraordinary 74 on Friday which saw him nab six birdies only to negate them with three double bogeys.
Leading second round scores in the French Open at the par-71 Golf National on Friday:
138 - Victor Dubuisson (FRA) 68-70, Martin Kaymer (GER) 69-69, Rafael Cabrera Bello (ESP) 68-70
139 - Francesco Molinari (ITA) 70-69, Tyrrell Hatton (ENG) 71-68, Daniel Brooks (ENG) 73-66, Jaco Van Zyl (RSA) 68-71, James Morrison (ENG) 71-68
140 - Felipe Aguilar (CHI) 71-69, Maximilian Kieffer (GER) 70-70, Bernd Wiesberger (AUT) 68-72 141 Brendan Steele (USA) 72-69, Andy Sullivan (ENG) 71-70, Kristoffer Broberg (SWE) 72-69, Gregory Bourdy (FRA) 69-72, Mikko Korhonen (FIN) 70-71, Mark Foster (ENG) 70-71
142 - Scott Hend (AUS) 70-72, Thomas Bjorn (DEN) 74-68, David Lipsky (USA) 71-71, Marcel Siem (GER) 69-73, Gary Stal (FRA) 73-69, Marcus Fraser (AUS) 73-69
143 - Richie Ramsay (SCO) 71-72, Damien McGrane (IRL) 73-70, Lasse Jensen (DEN) 72-71, Jorge Campillo (ESP) 70-73, Andrew Dodt (AUS) 69-74, Peter Hanson (SWE) 72-71, Fabrizio Zanotti (PAR) 73-70, Carlos del Moral (ESP) 72-71, Chris Lloyd (ENG) 71-72