The volunteer lifeboat crew were called into action at 16.24pm following a report from the Irish Coast Guard.
The yacht was on passage from Arklow when engine trouble flared just outside Bray Head.
As the country is experiencing a heatwave, weather conditions were near perfect with clear blue skies and good visibility.
The lifeboat crew quickly arrived on scene and successfully towed the yacht and skipper, who was uninjured, safely back to Dun Laoghaire Harbour.
Commenting after the callout, Dun Laoghaire RNLI coxswain Kieran Colley said: “The skipper of the vessel indeed made a good decision in calling for assistance. He was also wearing a lifejacket, which I’m always glad to see. I can’t stress enough how important it is to wear one.”
Winds were northerly Force 1/2 and visibility was very good when the lifeboat launched at 6.47pm, arriving on scene just four minutes later.
The lifeboat crew — helm Eleanor Hooker, Dom Sharkey and Joe O’Donoghue — found the two adults and three children on board to be safe and unharmed, and wearing their lifejackets. The skipper of the cruiser had dropped anchor to prevent drift.
The cruiser had engine failure that required specialist attention and so the lifeboat volunteer took the casualty vessel under tow to Garrykennedy Harbour, where it was safely tied alongside at 7.13pm.