The two leaders, fresh from a meeting in Paris to coordinate positions ahead of the summit over the debt crisis, decided to take the high-speed train to cover the 300 kilometres (186 miles) rather than fly.
Under tight security, the pair travelled from Hollande's office in central Paris to the Gare du Nord station and were due in Brussels later on Wednesday after the approximately 90-minute trip.
The travelling methods of Hollande, who dubbed himself "Mr Normal" during his recent presidential campaign against Nicolas Sarkozy, contrast sharply with his predecessor.
Sarkozy and his team of advisers would use two aircraft to get to Brussels from Paris, an Airbus A330-223 specially equipped for his use and dubbed "Air Sarko One" and a Falcon 7X.
The closely watched summit of the 27 EU leaders was expected to deal with ways of bolstering growth in the eurozone amid fears that debt-wracked Greece may be forced out of the club.