The Belfast woman took bronze after beating Canadian Audree Francis-Methot in the -52kg category.
The 25-year-old won her first match against Sinothanda Mva of South Africa by Ippon after only one minute and 43 seconds but was beaten by English competitor Kelly Edwards in their semi-finals.
Speaking afterwards, she said: "I'm delighted to win the medal and the first in judo since Lisa Bradley twelve years ago and so happy to win the first for Northern Ireland at these Games.
"Hopefully this will give my judo team mates a wee boost and the rest of Team Northern Ireland. It's very special to get the first one."
Sports Minister Carál Ní Chuilín has congratulated Kearney on her success.
"Lisa is the first local athlete to win a medal, and I am pleased that she has taken bronze in the 52kg category. It is a fantastic achievement for a Belfast sportswoman who has proven herself among the best martial artists in the world.
"It has been an action packed opening day at the Commonwealth Games, and I congratulate all the athletes who have taken part in the games so far. I also wish every success to those getting ready to compete."
Earlier in the day, Aileen Reid finished sixth in the triathlon as the first events of got underway.
The 32-year-old from Co Londonderry had been in the leading group as the race reached its final stages, but eventually lost out to Jodie Stimpson of England, who claimed the first gold medal of the Games.
Speaking afterwards, Reid said: "I'm pleased I gave it everything I had - I mean sixth, I can't turn my nose up at that and the girls that were there today were world class."
Team NI swimmer Sycerika McMahon reached the semi-finals of the 50m breast stroke after she was the fifth fastest qualifier with a time of 31.12 seconds, while Gemma Kane is into the semi-final of the 100m butterfly and Jordan Sloan has qualified for the final of the 100m back stroke.
There was also success for the men's lawn bowls triples team of Paul Daly, Neil Mulholland and Neil Booth as they were 21-23 winners against Kenya.
However the NI netball team were beaten 71-50 by Malawi, despite a strong start.
Noleen Lennon said: "We got off to a really good start but they had such a strong finish. It was a great experience, a great buzz!"
Michael Craig lost out in three games in squash to by top ranked Indian player Harinder while in badminton, Ciaran and Sinead Chambers were defeated by Chris and Gabby Adcock of England.
In men's table tennis, Northern Ireland won their first match against Guyana.