Senior attacker Yoshi Andersen powered her way for a game-high six goals and junior utility Melena Masson added three goals for the Breakers. Single goals were scored by senior defender Jessica Shusko, senior utility Jessie Holechek and sophomore attacker Lexie del Toro.
Goalie Etianne Manetta had eight saves and a steal.
"Mater Dei is a very good team and a very good program, so anytime you beat them it's a good win," Laguna Coach Ethan Damato said. "They played very hard and challenged us at each end of the pool.
"I thought we controlled the tempo of the game, limited their opportunities and we were able to get good shots each trip down the pool. In the end, we saw some areas that we need to improve on and I'm confident that we will."
Next week, Laguna goes up against Sunset League teams Edison and Fountain Valley which are ranked eighth and 10th, respectively, in the Division 1 poll.
The Breakers host Edison at 3:15 p.m. Tuesday and Fountain Valley at 3:15 p.m. Thursday.
They'll play Agoura, the top-ranked team in Division 2, Dec. 18 at Cal Lutheran University.
"We are looking forward to the Edison game next week," Damato said. "Every year we have a great game with them and I'm expecting that this year will be more of the same. Being that we are now in the same division, I think both teams will be a little extra excited. Should be fun.
"Fountain Valley will be another great Division 1 match up for us and another opportunity to learn about ourselves and improve."
Laguna played host San Juan Hills to a scoreless tie in nonleague play Dec. 3, two days after the Breakers opened the season with a 4-1 win at Sage Hill.
"I was extremely proud of the boys for giving a very mature and controlled performance," Laguna Coach Dan Richards said. "In the build-up to the game, we worked a lot in training on our defensive shape and they showed great maturity throughout the encounter.