The volunteer crew were requested to launch by Belfast Coastguard to the nine-metre RIB with three people on board which had been losing engine power.
The all-weather lifeboat, Dr John McSparran, launched into a slight swell with light levels decreasing as the night closed in.
The lifeboat reached the anchored casualty boat and a volunteer crew member was put on board to establish a tow rope so that the lifeboat could bring the casualty boat into Carrickfergus Harbour.
One of the casualties from the boat was transferred to the lifeboat for some respite from the cold conditions of the open water.
Upon reaching Carrickfergus, the casualty boat was handed into the care of the Portmuck Coastguard team.
Larne RNLI lifeboat operations manager Allan Dorman said: “The casualty boat did the right thing by dropping their anchor and calling for help at the earliest opportunity.
“Being able to find the boat in daylight made it much easier for our volunteer crew to establish the tow and bring them into the safety of Carrickfergus Harbour.”