"I'm pretty rapt to get my name on the trophy and hope I can go on to have the same success as some of them," An said.
He started the round with a six-shot buffer on the pack and was soon eight ahead with birdies at the 4th and 5th, although dropped shots pushed him back to even par at the turn, with three more bogeys on the 11th, 16th and 18th.
No one made a charge at the Kiwi international but An said there were still nerves.
"I was a bit shaky there for a while but eventually got the job done. I lacked course management a bit today and maybe was too eager and a bit nervous as well, although I shouldn't have been.
"A lead that big was going to be hard to muck up."
An rated Omokoroa's greens highly and said the back tee blocks on some of the holes presented a stiff challenge. He was the only golfer to finish under-par for the 54 holes, justifying his decision late last year to quit school at Takapuna Grammar and go full time with his golf.
Cho also held a six shot lead going into the final round and carded a one under par 71 yesterday for a four-under par total to overcome New Zealand teammate Julianne Alvarez.
The two time New Zealand amateur champion, who earlier this year won the Riversdale Cup and the Australian strokeplay, was happy to get back in the winner's circle.
"Julianne was playing nicely which put pressure on me. I made birdie on the 10th to her bogey which helped me settle down and then I played very solid coming home."
The top three women were all New Zealand internationals with Cho (-4), Alvarez (+4) and Chantelle Cassidy (Tokoroa) finishing on five over for the tournament.
Men's under-19 scores (Omokoroa):
213 Sam An (Titirangi) 67 71 75
217 Jarrod Freeman (Australia) 71 73 73
218 Tyler Hodge (Levin) 73 73 72, Ryan Chisnall (Greenacres) 76 72 70
219 Jordan Bakermans (Christchurch) 72 75 72, Cameron Jones (North Shore) 72 72 75
221 William Howard (Rotorua) 71 75 75, Luke Toomey (Ngaruawahia) 80 72 69
222 Compton Pikari (Te Awamutu) 72 73 77
223 Tae Koh (Manukau) 74 77 72, Jonathon Ratcliffe (Akarana) 78 72 73
224 Peter Lee (Rotorua) 75 75 74, Nick Voke (Manukau) 74 73 77
225 Jason Yoo (Waitikiri) 78 73 74, Jin Myeong Hwang (Tauranga) 74 75 76, Cameron Neal (Otumoetai) 80 73 72
226 Michael McAuley (Russley) 78 74 74, Brayden Mazey (Boulcott's Farm Heritage) 75 77 74, Harry Yang (Pupuke) 75 73 78
227 Denzel Ieremia (Hamilton) 78 71 78, Brian Joe (Titirangi) 75 75 77, James Eng (Remuera) 73 79 75, Kieran Goodall (Maraenui) 78 77 72, Sanjay Modgill (New Plymouth) 76 77 74
228 Aaron Garnett (Muriwai) 80 72 76, Jayson Zulch (North Shore) 78 75 75, Jack Sullivan (Australia) 77 69 82, Trent Munn (Manawatu) 75 76 77
229 Matthew Spraggs (Boulcott's Farm Heritage) 71 79 79, Anthony Cope (North Shore) 74 76 79, Johnny Tynan (Titirangi) 77 78 74
Women's under-19 scores:
212 Cecilia Cho (Pakuranga) 73 68 71
220 Julianne Alvarez (Manor Park) 75 72 73
221 Chantelle Cassidy (Tokoroa) 74 77 70
226 Grace Senior (Rotorua) 83 71 72
227 Catherine Bell (Ashburton) 73 79 75
228 Mun Chin Keh (Pakuranga) 79 76 73, Liv Cheng (Manukau) 75 72 81
229 Caryn Khoo (Pakuranga) 77 75 77, Emma Clayton (Manawatu, NZ) 80 76 73
230 Keita Durie (Palmerston North) 75 80 75
232 Jesse Hamilton (Maungakiekie) 74 77 81