The volunteer crew were on the scene with the inshore lifeboat just eight minutes after launch, following an alert from passers-by who heard the kayaker calling for help at Walter Rock in the Strangford Narrows.
Directed by those members of the public, the lifeboat reached the casualty who had been in the water for between 15 and 30 minutes, clinging to his upturned kayak.
He was taken onboard the lifeboat and made comfortable before being returned to shore and passed into the care of Portaferry Coastguard. The lifeboat crew then returned to the Narrows to recover the kayak.
Speaking after the callout, Portaferry RNLI press officer Jordan Conway said: “We would like to commend the members of the public who raised the alarm last night which ensured we reached the casualty in good time.
“As the summer season continues, we remind everyone planning a trip to sea to always respect the water.
“Always carry a means of calling for help and keep it within reach. Wear a personal flotation device and check the weather and tides.
“Tell someone where you are going and when you are due back and always wear appropriate clothing for the conditions and your trip.”