The new route will be the only non-stop high-frequency flight between the capital and Cornwall when it comes into operation on February 15th.
Flybe has said that the service will operate three times a day on weekdays, daily on Saturdays and twice-daily on Sundays, with fares starting at £29.99.
Commenting on the new flight, Mike Rutter, Flybe’s chief commercial officer, said it was a "vote of confidence" in the county and the airport’s team.
"We realise the importance of maintaining affordable choices with a convenient multi-frequency schedule on this key business route," he said.
Flybe is now the third-largest airline at London Gatwick after adding new business flights to Aberdeen and Newcastle over the past year.
The airline announced last week that it would be re-introducing its Jersey and Exeter flights to supplement high-frequency routes from Edinburgh and Manchester.