The House voted 211-116 against the repeal.
"Live Free or Die is alive and well in New Hampshire," advocacy group Freedom to Marry's National Campaign Director Marc Solomon said in a statement. "Today's vote affirms that Granite Staters stand strongly against stripping away freedoms from any of their neighbors.
"Our opponents tried to abuse the 2010 Republican legislative sweep in New Hampshire to repeal the popular law. What they didn't count on was the fact that the freedom to marry is becoming a bipartisan value, as resoundingly reflected in today's vote," Solomon said.
The bill's main sponsor, state Rep. David Bates, a Republican, wanted voters to have their say through a non-binding referendum on the matter, the Manchester New Hampshire Union-Leader reported. New Hampshire does not allow binding voter referendums.
"In November we will find out once and for all, unequivocally what the citizens of New Hampshire want," Bates said last week.
Bates said his bill would have replaced the "illegitimate" definition of marriage with a definition that marriage is between one man and one woman. He said the measure also would replace same-sex marriages with civil unions; limit civil unions to eliminate the possibility of incest; eliminate religious or moral exemptions for employment, housing and public accommodations; and clarify that same-sex marriages entered into under the current statute would remain valid if the law is repealed.
Lawmakers approved civil unions in 2007 and same-sex marriages 2009. The Union Leader said 1,906 same-sex couples were married since the law went into effect Jan. 1, 2010.