The 34-year-old, who joined the British outfit in 2010, is expected to boost Vacansoleil's profile in the classics after a disappointing spring this year for the Dutch team.
Team manager Daan Luijkx said: "This spring we had a hard time getting results after Björn Leukemans got injured. We showed in stage races that riders like Thomas De Gendt and Wout Poels became world class but in the classics there is still a way to go for our young riders.
"Therefore we started looking for a rider who is capable of sharing his experience with young riders and who can ride finals himself.
"Flecha is, like Leukemans, someone who can be a captain on the road. To sum it up: this guy is world class for many consecutive years, has a great track record and brings experience from several top teams.”
Flecha, winners of the Omloop Het Nieuwsblad in 2010 and a stage of the 2003 Tour de France, said: "I had a great time at Sky but I see new chances at Vacansoleil-DCM which races a bit different.
"Vacansoleil-DCM is focused on stage wins and rides aggressively at many races. This way of racing will give me the chance to show what I am good at and I will try to get some wins in stage races and classics."