The addition of the Saturday flight from 6 June takes Icelandair to five weekly flights between Gatwick and Reykjavik.
The new flight is part of the airline’s plans for 17% capacity growth from the UK in 2015, which will also see it launch a twice-weekly service from Birmingham from 5 February.
Icelandair also operates from Heathrow, Manchester and Glasgow.
More airline news:
More on Iceland: