She was first elected in the 2005 election to the constituency of Esquimalt-Metchosin, garnering almost 50 percent of votes cast and 2,895 more votes than the next closest candidate. She was re-elected in 2009 to the new constituency of Esquimalt-Royal Roads and again in 2013.
In August 2007, Karagianis was appointed the Official Opposition Critic for the Ministry of Transportation in New Democrat leader Carole James' shadow cabinet. She had previously served as the Official Opposition Critic for the Ministry Children and Family Development, and, prior to that, the Ministry of Small Business and Revenue. Following the 2009 election, Maurine was again appointed as the Official Opposition Critic for the Ministry of Children and Family Development. In January 2011, Maurine was elected as Official Opposition Caucus Whip and presently continues to serve in this position. In June 2014, Maurine was appointed as Advocate for Seniors, Women & Childcare & Early Learning.
Prior to serving as an MLA, she was elected as a municipal councillor in Esquimalt in 1996, and re-elected in 1999 and again in 2002.
Starting in 1998, she served three years with the provincial government as assistant to three NDP cabinet ministers – first in the Social Services ministry and then in Transportation and Highways. From 2001 to 2005, she ran a consulting company working with non-profit organizations and First Nations to create seniors housing in BC.
She is an entrepreneur, opening her own retail fashion store, operating a wholesale venture and a successful import/export business. She was also a co-founder of the Sunshine Folkfest in Powell River, BC.