The Frontex agency will send out two Spanish boats from September to October, and then one from Lithuania up to January, to join French patrols, authorities managing the area said.
The Channel is one of the world's busiest shipping lanes, and many migrants have died in its strong currents trying to cross from France to Britain. Human traffickers regularly overload dinghies, leaving them barely afloat.
In August, French coastguards had to rescue 157 people from a boat that caught fire.
"In response to the ongoing migration crisis in the Channel, Frontex will deploy patrol vessels to complement temporarily French assets engaged in search and rescue operations," read a statement from the France-based Maritime Prefecture for the Channel and the North Sea.
Migration is one of Europe's most divisive political issues, including in Britain where the ruling Labour party is facing a challenge from the populist Reform UK party, which has vowed to stop migrants arriving in boats.
Britain said in April it would pay France up to £660 million ($892.72 million) under a three-year border security deal to curb illegal migrant crossings of the Channel, with part of the funding contingent on results.
Last year, both countries agreed a "one in, one out" pilot scheme under which France will accept the return of undocumented people arriving in Britain by small boats, in exchange for Britain agreeing to accept an equal number of legitimate asylum seekers with British family connections.
