Cao's "yes" vote ended up being unnecessary for House Democrats in the 220-215 tally, but as the only GOP member to support the bill, he gave House Speaker Nancy Pelosi license to tout bipartisan support for the controversial measure.
"I felt last night's decision was the proper decision for my district even though it was not the popular decision for my party," Cao, a first-term representative from Louisiana's traditionally Democratic 2nd District, told CNN.
"A lot of my constituents are uninsured, a lot of them are poor," Cao said. "It was the right decision for the people of my district."
The first Vietnamese-American to serve in the House, Cao defeated nine-term Democratic incumbent William Jefferson in last year's election. Jefferson was under indictment on money laundering and bribery charges at the time, and has since been convicted.
Cao, a devout Catholic, said Sunday that an amendment to strengthen anti-abortion language in the House bill cleared the way for his support.
"When that was worked out … I called the White House and said I could possibly support the bill," said Cao, adding he discussed getting continued help for his district as it seeks to fully recover from the impact of Hurricane Katrina.
Asked about the reaction of fellow Republicans to his vote, Cao said the party's leaders "respect my decision, and I respect theirs."
"To tell you the truth, neither one of us really knows what is the right decision," he said of the complex health care bill, citing differing reports and differing studies on its impact. "Ultimately, we have to make that leap of faith."
The bill's approval by the House late Saturday night marked a major step for Obama's top domestic priority. If the Senate now passes its own version, the two bills would be merged, and the final version would require approval from each chamber before being sent to the president for his signature.