Sorenstam finished the tournament at 8-under-par 208 for her 67th career title. Her win here last year was the first of 10 on the season, and also the first of three straight.
Last year's overwhelming money leader, Sorenstam collected $180,000 for this win.
'I remember playing well last year, but this year it came down to the last few holes. It was just a loaded leaderboard, so that made it really tough,' said Sorenstam.
Helen Alfredsson fired a 5-under 67 to finish tied for second place with Seon Hwa Lee at 7-under-par 209. Lee shot a 70.
Still looking for her first LPGA win, Natalie Gulbis held the clubhouse lead for a while after a final-round 66 put her at minus-6. But Gulbis finished tied for fourth place with Paula Creamer (72) and Mi Hyun Kim (72), who had shared the second-round lead with Sorenstam.
Gulbis' 66 was tied for the low round of the day with Katie Futcher, who shared seventh place with Suzann Pettersen at 5 under, and Virada Nirapathpongporn, who tied for 15th at minus-1.
'I think if I just keep giving myself chances throughout the year, it'll happen for me,' Gulbis said of the prospects of getting her first win.
On the other end of the spectrum is Sorenstam.
After skipping the first two LPGA events of the season, the dominating Swede hadn't played competitively since the Women's World Cup of Golf in January when she teed it up for her first round Friday.
She was less than rusty.
Sunday was Sorenstam's third round under par. She survived a bogey on the front nine that dropped her from the top spot, but later regained the lead with consecutive birdies at the 12th and 13th.
At 13, she rolled in a 15-foot putt for the birdie.
'That was a big putt,' she admitted. 'I really pulled out some clutch shots when I needed to. That is why I love doing this. Coming down the stretch and hitting those shots, there is nothing better.'
Another birdie at 15 moved Sorenstam to 9 under. She led by two shots at that point, so a bogey six at the 18th meant nothing.
Mexican Lorena Ochoa played in front of a supportive crowd, but struggled to her second 74 and ended tied for 34th place at plus-2.
'It's a dream to win here in my country,' Ochoa said as fans chanted her name in the background. 'So, we'll see.'
Suzann Pettersen shot a 4-under 68 to tie Futcher for seventh place at minus-5. Cristie Kerr (72) and Tina Barrett (68) were one stroke further back in ninth.