"This is legislation that doesn't achieve what I think we need it to achieve," Matheson said in an interview. "I think we need to create a sustainable future for our health-care system and control these costs, which are growing at a rate that isn't sustainable. I think it's time to start over and do it right."
Utah's Republican representatives, Rob Bishop and Jason Chaffetz, also voted to repeal the law, dubbed "Obamacare."
Matheson, who faces a tough re-election fight this year against Saratoga Springs Mayor Mia Love, said he's being consistent in his votes against the Democratic-written law.
"This is an issue that's been very divisive and has got a lot of strong emotions on any side of the issue, but I've been very consistent," Matheson said. "When it came up in committee, I voted no. When we voted on the House floor, I voted no. When the Senate brought it back to the House, I voted no, so there's nothing new here."
But Love seized on a procedural vote Tuesday night in which Matheson voted against considering the repeal measure as proof her rival doesn't really want the law tossed.
"As expected, Jim Matheson once again made a vote of political expediency," Love said in a statement. "Today, he stuck his finger in the wind and voted 'aye' in a desperate attempt to save face and save his job in November."
Wednesday's vote was the first since the U.S. Supreme Court upheld the law and Congress' power to force Americans to buy health insurance or pay a tax but Matheson noted that the court ruled only on the act's constitutionality, not its effectiveness.
Less than an hour after Wednesday's vote, the National Republican Congressional Committee criticized Matheson's support for repealing the law with an email subject line of "somebody's getting scared." But if Matheson had voted the other way, he would have been vulnerable to accusations of flip-flopping.
On the other front, Matheson's vote could irritate Utah Democrats who back the health care law and alienate a key base of supporters.
Matheson faced a Democratic primary in 2010 amid complaints he was too conservative.
Noting that some Utah Democrats oppose the health-care overhaul, Matheson argues voters will look at his overall record.
"At the end of the day, I'd like to think we share the same goal," he said, "and that's to create a better, sustainable health-care system."
The House-passed repeal stands zero chance of clearing the Democrat-controlled Senate, though it's one of a slew of bills GOP leaders plan to bring up this month to create fodder for the fall elections.
Chaffetz said it was good to put members of Congress on record.
"Obamacare is the wrong prescription for the country," he said. "We definitely need reform with health care, but this was never the right bill."
Bishop, too, applauded the repeal vote as a step toward reining in the federal government.
"Obamacare is one of history's most egregious examples of federal overreach," he said. "Our Founding Fathers would be horrified by the bill's assault on individual freedom and liberty."
Andreas Rivera contributed to this story.