Hailey Bieber Spotted in Tiny Black Dress While Leaving Party with Justin

Justin and Hailey Bieber might be giving fans a little déjà vu ... 'cause they left another one of Justin's album release parties together -- and Hailey commanded attention in an eye-popping outfit.

The singer-songwriter and his model better half left the party in NYC together Friday night ... JB's hand resting on Hailey's hip as they headed out into the concrete jungle.

Check it out ... Justin's dressed casually in a T-shirt featuring cartoon cats -- while Hailey's dolled up in a tiny black dress with lace details that give it a lingerie vibe.

The Rhode founder flashed a smile while hopping into the car ... though Justin appeared more pensive -- perhaps thinking about how the new 23-track release was received. Alix Earle, Lori Harvey, and a ton of other celebs attended the event, too.

If you're getting a familiar feeling in the back of your head, you ain't the only one ... we saw these two leaving a party for Justin's "SWAG" at the end of July -- holding hands on the way to their car.

Justin stood out in a bright pink hoodie at the time ... while Hailey tossed on a slightly more conservative, less leggy outfit.

As we told you ... Bieber heaped praise on Hailey in "SWAG II" -- vowing to always stay with her and to never let her down. He also says their son, Jack Blues, has all of Hailey's grace inside him on the track "MOTHER IN YOU".

He peeled the curtain back a bit on the difficulties in their marriage, as well -- similar to some tracks on "Swag."