The massive ship was launched in Belfast on May 31, 1911 from Harland & Wolff, then the largest shipyard in the world.
During the ceremonies, a flare was fired at 12:13 p.m. local time, the exact time of the launch a century ago, the BBC reported Tuesday.
A religious service was held on the site of the slipway from which Titanic was launched from the shipyard.
The congregation heard music from two choirs historically involved in the life of the shipyards, and observed a moment of silence in remembrance of the 1,517 people who died on the ship's disastrous maiden voyage.
Reverend Chris Bennett, who led the service, said he wanted celebration to be the mood of the event.
"For the last 100 years Titanic has often not been mentioned," he said. "It's been our shame, our secret.
"We've almost had a hundred-year moment of silence, so really we're trying to rediscover the pride today."
Wisconsin business offering 'therapeutic cuddling' forced to close
Megyn Kelly: Santa Claus and Jesus are both white men