The club was started in 1980 by Pat Vincent, a former Captain of the New Zealand All Black rugby team, after he moved to take up a teaching position in California in 1967, where he was offered a rugby coaching job at St Mary's College. He was well respected for his rugby playing and singing ability. Pat Vincent captained the All Blacks in 1956 in a two test series against the formidable South African Springboks. 

The first Lamorinda High School team was known as the Vincent’s and, as was custom in those days, the second side adopted an amusing and derogatory name: the Rodents. This was reportedly due to the 2nd Team Coach affectionately calling his charges "Rodents". When the majority of the Vincent’s team graduated in 1981, the Rodent players became the core of the first team and they decided to retain the name. Pat Vincent coached until 1983 when he tragically died of a heart attack on an airplane returning from Scotland where he had been on tour with his St. Mary’s Rugby Club. 

Around 1989, John Donohue designed the first Rodent logo, and in 2011, Matt Taylor added a new logo. Lamorinda went to the 1998 National High School Championships in Indianapolis, Ned Anderson was the Head Coach, and Doug Cole and John Dixon were the Assistant Coaches. The team took the red eye out of SFO Thursday night and got into Indianapolis in the early hours on Friday morning. Lamorinda traveled the furthest and had the first 25 minute match vs. the Worthington Worms bright and early Saturday morning. Lamorinda lost that match by a conversion, but won the next 4 matches, which included a 40 minute match Saturday late afternoon and a 70 minute match Sunday, and ended up taking 5th in the nation. The Worthington Worms lost to Highland RFC in the semi-final and ended up 4th in the Nation.

Between 1980 and 2001, Lamorinda was purely a High School team and at the start of each season the coaches and players had to go out and recruit players to make up a team. In 2002, Tony McKenzie presented an expansion plan to the Club’s Management team. The purpose of this plan was to create a flow of players into the High School program so that we would not have to re-invent the wheel every season.

Under the direction of Tony McKenzie, the Youth program got under way in 2003, with it's first Under 14 team headed by Glen Dickens. In 2004, the Youth program was expanded to include an Under 12 and Under 10 program that was Coached by Matt Taylor. As a result of Lamorinda’s success in establishing a Youth Rugby Club, many other Northern California Rugby Clubs modeled their expansion programs on Lamorinda. The club added an Under 8 program in 2005.

Lamorinda was instrumental in helping establish the Northern California Youth Rugby Association (NCYRA) in 2010, which now governs Youth Rugby in Northern California. The Club continues to be an active contributor, influencer and participant in the NCYRA by serving on the Board and on the many sub-committees that govern rugby in Northern California.

In 2012, Lamorinda was crowned the Northern California High School Club Champion and went on to win the first California Cup by beating Oceanside RFC, the Southern California High School Club Champion, in a fiercely contested and high spirited game. The final score was 27-17.  The same year, Rugby Magazine ranked Lamorinda RFC #1 in California and #2 in the Nation.

The club has a rich history of touring to England, Wales, Ireland, Canada, New Zealand, Argentina, Hawaii and Pacific North West. They have also hosted numerous international touring teams from Australia, England and Canada as well as local teams from Los Angeles and the Pacific North West.