The flight was heading to Sharm el Sheikh in Egypt with 188 people onboard when a cabin pressure warning light came on shortly after take-off from Cardiff.
The pilot immediately dropped altitude to 10,000ft and circled Dover before making an emergency landing at Gatwick.
A spokesman for Thomson indicated that the light had come on owing to a technical fault, as he revealed there had been no loss of cabin pressure and oxygen masks were not required.
The spokesman added: “Flight TOM532 was diverted to Gatwick Airport as a precautionary measure after a faulty cabin pressure light came on during the flight.
“The plane landed safely at 10.20am at Gatwick and all passengers were placed on another plane to continue their journey to Egypt.”