A task force led by the Royal Navy has seized drugs worth nearly £400 million from smugglers.
Sailors made eight raids over a five-month period, netting 1.75 tonnes of narcotics.
The haul included 265kg of heroin and 455kg of hashish worth £65 million, which was seized by those manning HMS Monmouth - a Type 23 frigate.
The UK and France commanded the multinational naval task force, which polices more than three million square miles of sea in the Gulf and Indian ocean.
British, French, American and Australian warships took part in the operation to counter drug trafficking, which funds terrorism in the region, the Ministry of Defence said.
Defence Secretary Sir Michael Fallon said: "The success of this joint task force with our French allies is a demonstration of Britain's firm commitment to global maritime security and our ability to work with European allies to tackle the threat from drug smuggling.
"The money made from these nefarious criminal activities fund the terrorists who threaten us at home and abroad. As we leave the EU we will continue to work alongside our allies to tackle smuggling in the region and maintain the free flow of shipping."
Combined Task Force 150 (CTF150) aims to track down vessels smuggling drugs and weapons, as well as deterring maritime terrorist activity in the region, which includes trade routes such as the Suez Canal.
Navies from the Combined Maritime Forces, a coalition of 31 nations, take it in turns to lead the task force from either a command ship or the headquarters in Bahrain.
The Franco-British group took over operations from the Canadian navy in April and has recently passed on command to the Pakistan navy.
Royal Navy Captain Paul Pitcher, CTF's Deputy Commander, said: "The deployment of a combined French-UK staff has successfully demonstrated French-UK naval integration in an operational maritime environment.
"The ships under our command have enjoyed considerable success in seizing illegal drugs at sea, as well as providing naval presence to reassure the shipping community in and around the strategic choke-point of the Bab Al Mandeb Strait."