“Dreams come true,” Noh told reporters after collecting $1.
224 million for his first tour victory.
He always held at least a share of the lead during the final round and finished at 19-under 269, while Americans Andrew Svoboda (69) and Robert Streb (70) tied for second on 17-under.
Noh won at the same tournament where trail blazer K.J. Choi 12 years ago became the first Korean to win on the PGA Tour.
Choi now has eight victories, while countrymen Yang Yong-eun (two) and Bae Sang-moon (one) have also won.
American Kevin Na, who was born in South Korea but moved to the U.S. at a young age, also has one victory.
Noh was home in Korea visiting family when the ferry sank on April 16.
He was in a sombre mood as he heard the news unfold, but returned to the U.S. soon afterwards to refocus on his golf.
“All the TV, all the people, everything focus on ferry and then all the people very quiet down, so same as me,” said Noh, who has thought about winning at the highest level since he was a boy.
“When I start playing golf at age seven always my dream is playing PGA Tour, playing major championships, but my dream’s come true today so I’m really really happy now.”
Noh arrived in the Big Easy ranked 176th in the world, but his lowly status belied his recent consistent form and his victory was not the huge shock it might appear to some.
He negotiated the first 54 holes without dropping a shot to take a two-stroke lead over American Keegan Bradley into the final round.
A bogey at the first hole ended his unblemished streak, and after two holes he had fallen into a three-way tie for the lead with Bradley and Streb.
Bradley subsequently fell away with a triple-bogey at the sixth hole and then Streb double-bogeyed the par-three ninth after hooking his tee shot into a water hazard.
But Noh could not breath easily until he birdied the 16th hole from three feet after nearly holing his approach shot.
A 12-foot par save at the par-three 17th then allowed him to enjoy a victory march down the last.
(Reporting By Andrew Both in Cary, North Carolina, Editing by Gene Cherry/Greg Stutchbury)