Parker claimed victory after her biggest challenger, former Houston City Attorney Ben Hall, took to a stage minutes before to concede the race.
"I love this city. Tonight, I feel like it loves me back, so thank you for the very warm welcome. Thank you. Thank you to the many people who made this victory possible," Parker said. "I want to make Houston an even better place to live, work and raise a family. I thank my family for the great support that they always give me but the amount of time they've taken to run the campaign."
Hall's concession came after only 8 percent of precincts reported Parker had taken 50 percent of the votes. But as more votes poured in, Parker's lead continued to grow.
"We may not have enough votes to be the next mayor of the city of Houston, but that does not end this journey, that does not end our love for this great city. And it definitely does not end our appreciation for all your hard work and all of the efforts that you have given to make this campaign competitive, to make sure that all the issues are addressed, to awaken the mayor's office to the concerns of the entire city," Hall told his supporters. "If nothing else, we have spoken on behalf of the dreams and aspirations of a great people."
Seven other candidates, including attorney Eric Dick, were challenging Parker, but none of them garnered enough votes to force her into a run-off election.
Parker was first elected in 2009. She won her second term in 2011 in a close election in which she held off five challengers. Term limits prevent Parker from running for a fourth term.
During Parker's administration, Houston weathered the recent recession better than most major cities and in various surveys Houston has been named as one of the best cities to live in.
With Parker's re-election, Houston, which has about 2.1 million residents, continues to be the largest city in the United States led by an openly gay person.
During her campaign, Parker touted her administration's work in balancing the city's budget during the recession without raising taxes and without laying off police and firefighters. She also said Houston's overall crime rate is down 8 percent compared to the three years prior to 2010.
Hall had charged that Houston has become less safe and less economically sound under Parker's administration.
The Associated Press contributed to this report
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