Down three runs with two outs in the seventh inning, Northwestern was one out away from losing to rival Northern Lehigh and falling 0-2 in Colonial League play.
But the Tigers got three quick hits, including back to back home runs by Brooke Heller and Cailie Rehrig for an 8-7 win.
"We had our heads down a little bit in the middle innings, but we knew what we had to do," said Rehrig after her walk-off solo home run. "We knew we could do it. We have big hitters. We had the top of the line up up."
Lauren Horner started the late rally with a one-out single in the bottom of the seventh. She scored on Blaise Barron's two-out single to get the Tigers within 7-5.
Heller, a senior who had a walk-off home run against Northern Lehigh last season, hit the tying shot this time, making it 7-7 with sophomore Rehrig headed to the plate.
She took a 2-2 pitch to left center field and circled the bases just ahead of the throw.
"It's my first year starting varsity," said Rehrig, who was 2 for 3 with 3 RBI in the game. "It's a very big hit for me. It's definitely the biggest hit of my career.
Northwestern saw a three-run lead disappear in the fifth, but wrested momentum back just in time.
"I'm so proud of the comeback I can't express it in words," said Northwestern head coach Jen Horner. "That's a remarkable win. You don't see a comeback like that every day."
The Tigers' two homers in the seventh were the fifth and sixth home runs of the game.
Lauren Horner led off the bottom of the first inning with a home run. The Bulldogs Amber Kibler matched it in the top of the second, tying the game at 1-1.
Northwestern got the lead back in the third inning. Ashley Eden led off the inning with a single. Heller and Rehrig came up with two-out singles, with Heller driving in one and Rehrig two for a 4-1 lead.
Northern Lehigh came back with a five-run fifth inning. They scored a run on a wild pitch just before Sarah Frantz hit a two-run homer to make it 4-4.
A Shannon Weil single and a Cassie Toth's home run gave the Bulldogs a 6-4 lead. They added another in the sixth on a walk followed by a throwing error on a bunt.
"Our hitting was a huge confidence boost today," said Northern Lehigh head coach Jon DeFrain. "It's all about timely hitting and that's what they got at the end there.
"It was a tough way to lose one. It was back and forth the whole time. You have to give credit to Northwestern. We had two outs and were ready to put them away and they got the hits."
No. Lehigh 010 051 0 – 7 7 0
Northwestern 103 000 4 – 8 9 1
Horvath and Filchner; Bennett, Eden (5) and Williams. W – Eden. L – Horvath. HR: NW – Horner (1st, none on), Heller (7th, one on), Rehrig (7th, none on); NL – Kibler (2nd, none on), Frantz (5th, one on), Toth (5th, one on).