The unnamed climber, who used no harnesses or other aids, was detained after he got to the top of the 210-metre (690 feet) office block, the source said.
He began the ascent in the early evening and was arrested at 8:00 pm (1800 GMT) after a rescue worker descended on a rope and accompanied him to the roof of the tower.
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It wasn't the first time a climber had taken on the Tour Montparnasse. In 2015 the French “Spiderman” Alain Robert completed the daring feat with a Nepalese flag in hand, in tribute to the victims of a devastating earthquake in the country.
The Tour Montparnasse is not as high as the famous Eiffel Tower but remains the only skyscraper in the Paris city centre.
The security services' DOPC intervention and protection group (Gip) abseiled down to reach the man.
Francois MALIGORNE / AFP