NU recovered from a sloppy third set where it committed 15 errors.
The Lady Bulldogs also crawled their way back from a 19-16 deficit in set four before Bella Belen and Ivy Lacsina put on the finishing touches.
NU takes the early lead.
"Siguro in terms of preparation, yun lang ang naging malaking bagay sa amin," said coach Karl Dimaculangan, still unhappy with the error-prone ways his teamhad as they gifted 38 easy points to the Blue Eagles.
"Yung errors namin yung nagiging problema namin. Marami pa kaming dapat ayusin."
Bella Belen got 18 markers from 16 hits, Alyssa Solomon chipped in 15 points, and Lacsina had 12 in the victory.
Jennifer Nierva had 20 excellent digs and 13 excellent receptions.
It was a massive win for a promising NU squad aspiring for a crown, scoring its first win over Ateneo since February 2018.
Faith Nisperos bannered Ateneo, winless in two matches, with 16 points with 19 excellent receptions and 10 excellent digs.
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