The win was Ward's fourth on the LPGA Tour and her first since the 2001 Wendy's Championship for Children.
Ochoa gave Ward a run for the title, but her final-round, 7-under 65 came up just short. She finished at 14-under-par 202.
Shi Hyun Ahn matched Ochoa's course record on Saturday with a 9-under-par 63. She tied for third place with Paula Creamer, who carded a 65, at 13-under-par 203.
Ward, who brought a three-shot advantage into the final round, wasted little time in breaking into red figures. She hit a 58-degree wedge to 3 feet to set up birdie at the second.
At the par-5 sixth, Ward's 3-wood approach landed in a greenside bunker. She blasted out to 10 feet and canned the birdie putt. Ward added another front-nine birdie, at the par-5 ninth. She laid up short of the green, then wedged her third to 6 feet.
As well as Ward was playing, Ochoa continued to close the gap. Ochoa tallied three birdies in a row from the fourth, including a two-putt from 20 feet at the par-5 sixth. She completed her front nine with a two-putt birdie at nine after she found the green with a 6-iron.
Ochoa went on another birdie run around the turn. She notched her second birdie in a row at the 10th when her 4-footer found the bottom of the cup. Ochoa collected her third consecutive birdie at 11 after she ran home a 15-footer.
Ochoa was now within one, but Ward extended her lead at the 12th. Ward hit a pitching wedge to 8 feet to set up birdie, then both players birdied the 16th from close to 12 feet.
Ward held a two-shot lead as Ochoa, who played in the group ahead of Ward, came to Las Vegas Country Club's closing hole. She ripped her drive down the fairway, then choked down on a 5-wood for her second. Ochoa's ball stopped 25 feet from the hole on the fringe.
Ochoa, needing eagle to tie, came up short with her eagle chip. She had 4 feet for birdie, but missed that putt as well, meaning Ward had a two-shot lead with the par-5 to play.
Ward played conservatively and made par, but collected the title.
'I only had a couple of bogeys all week,' said Ward. 'That's what probably makes this week a little more special than some of the other ones. It was just a very consistent week.'
Ochoa collected her second runner-up finish and third top-5 this season. She has yet to visit the winner's circle in 2005, but Ochoa just had too much ground to make up on Saturday.
'I did everything I could,' said Ochoa, who was nine back after one round and four behind after two. 'Wendy just had a great day. It was a great experience and I am pretty happy.'
In-Bee Park, a 16-year-old amateur, posted a 5-under 67 and took fifth place at 12-under-par 204. Juli Inkster, who is 28 years older than Park, also carded a 67 and came in sixth at minus-10.
Moira Dunn, who was tied for second heading into the final round, shot a 1-under 71 and tied for seventh with Nicole Perrot (70) and Jeong Jang (65). The trio was knotted at 9-under-par 207.
Karrie Webb, who shared second with Dunn on Friday, struggled to a 1-over 73 and tied for 16th place at minus-7.