2006 In August, at the age of 11, Maguire beat more than 800 competitors from 30 countries to become the winner of the under-12 World Golf Championship at Pinehurst in North Carolina. Her twin sister Leona Maguire came third. In September, the twins were chosen to bring the Ryder Cup trophy to the stage during the presentation ceremony after Europe's win at the K Club against the USA.
Maguire won the Midland Girls Championship; Ulster Girls Championship; Leinster Girls Championship; Ulster U-19 Schools Championship; Girls Interprovincial Championship; Ulster Girls Order of Merit title; Irish Girls Order of Merit title; Runner-up in Connacht Girls Championship; Semi-finalist in the Irish Ladies Close and Semi-finalist British Girls Championship.
On 21 May, Maguire was runner-up to her twin sister Leona in the Lancome Irish Ladies Close Championship at Westport, County Mayo. On 19 July, the positions were reversed when Lisa triumphed over her sister 4 and 3 in the final of the Lancome Irish Girls Close Championship at Mullingar Golf Club. It was the first time in the history of Irish Golf that the Irish Champions of both the Women's and Girls events come from the same family let alone twin sisters. On 26 July, she beat her sister Leona by four shots in the European Young Masters final at Chantilly, France. As a result, both twins were picked for the European Junior Ryder Cup Team which later lost to the USA at Olde Stone, Bowling Green, Kentucky on 17 September. In December, she and her sister Leona were named jointly as the Women's Amateur of the Year at the AIB Irish Golf Writers' awards for 2008.
On 26 April, at the age of 14, Maguire came third in the Helen Holm Scottish Women's Open Amateur Strokeplay Golf Championship played at Troon Portland and Troon Old Course. Her sister Leona won the event after a final round score of 73 for a 54 hole aggregate score of −6, 219. On 20 May, she defeated Mary Dowling of New Ross Golf Club by a 5&4 margin in the final of the Lancôme Irish Women's Close in Fota Island. On 21 June, she did the Irish double by winning the Irish Women's Open Strokeplay following a play-off with Hannah Burke after both finished 5-under-par for 54 holes at Douglas Golf Club. On 11 July, the twins were part of the four girl Ireland team which defeated Sweden 4–1 in the final of the Girls' European Team Championships at Kokkola, Finland to become European Champions for the first time in Irish golfing history. She played for Great Britain and Ireland in the Vagliano Trophy in July, becoming the second youngest player at the age of 14 ever to represent the side, along with her twin sister Leona who was the youngest player by 15 minutes. The twins were the joint top highest scorers for the GB & I side which lost to Europe 13–11. Both twins were selected for the 2009 Junior Solheim Cup Team at the Aurora Country Club, Illinois, USA in August. In December, she was named as the Women's Amateur of the Year at the AIB Irish Golf Writers' awards for 2009.
Maguire played for Great Britain and Ireland in the Curtis Cup in 2010, becoming the second youngest player at the age of 15 ever to represent the side, along with her twin sister Leona who was the youngest by 15 minutes.
In March, Maguire won the Spanish Ladies Open Amateur Champion in Cádiz and in July she won the European Ladies Amateur Championship at the Noordwijk Golfclub in the Netherlands, becoming the first ever Irish winner. She was chosen along with her sister Leona in the European side which earned a 12–12 draw against the USA in the PING Junior Solheim Cup at Knightsbrook in Meath on 21 September. In December, she and her sister Leona were named jointly as the Women's Amateur of the Year at the AIB Irish Golf Writers' awards for 2011.
Maguire left secondary school at Loreto College Cavan in Ireland with top scholastic honours and joined Duke University in Durham, North Carolina, U.S.
On 6 July, Maguire was named on the The Women's Golf Coaches Association (WGCA) 2015 All-American Scholar Team.
On 24 May Maguire won the Ulster Women’s Open Championship at the Royal Belfast Golf Club in Ireland. She registered four match play wins after finishing second in stroke play qualifying with rounds of 76 and 77. On 7 July 2016 she was part of the Ulster team which won the 2016 Ladies Inter-provincial Championship for the second straight year at the Slieve Russell Golf Club in Ballyconnell, County Cavan. On 2 November she helped Duke win the East Lake Cup held at East Lake Golf Club in Atlanta, Georgia, USA, beating Washington State in the final.
At the LSU Tiger Golf Classic held at University Club in Baton Rouge, Louisiana, USA on 26 March, Maguire hit the first eagle of her college career. On 5 July Maguire was selected for the Women’s Golf Coaches Association (WGCA) All-American Scholars Team for the second time in her career.
AmateurJunior Ryder Cup (representing Europe): 2008
Junior Solheim Cup (representing Europe): 2009, 2011
Vagliano Trophy (representing Great Britain & Ireland): 2009
Curtis Cup (representing Great Britain & Ireland): 2010