The RNLI was alerted at 8.20am, local time, and sent out two all-weather lifeboats, with a crew from Ramsgate heading out first before a Dover crew followed minutes later.
HM Coastguard then joined the search deploying a helicopter and a search and rescue aeroplane with high-tech radar capabilities.
The cruise ship is understood to have turned around after realising that a person had gone overboard. Tracking data shows the ship passing Lydd, on the south coast, at around 9.10am, local time, before turning around and heading back out past the east Kent coast.
A spokesman for the cruise line said: “AIDA Cruises confirms that there is reason to believe that a crew member of AIDAperla went overboard in the English Channel in the early morning of Oct 22.
“The captain and crew of AIDAperla immediately initiated all necessary rescue measures in close coordination with the local authorities. The search on board confirmed that a male crew member is missing.
“The ship was immediately stopped and returned to the spot where the incident was believed to have occurred. The search for the missing person is ongoing and has our utmost priority.”