For the two parties, Stefani was dressed up as a sexy cowgirl, while Shelton wore a poncho, fake beard, and trucker hat.
Later in the night, Shelton and Stefani hit Jared Leto's Halloween party, which was also attended by Leonardo DiCaprio, Fergie, and Josh Duhamel. At the end of the evening, they were seen leaving the party in the same car.
They met up with fellow "The Voice" coach Adam Levine at Leto's party and his wife Behati Prinsloo posted a snap of the trio on Instagram!
Gwen and Blake became a rumored item after each split from their mates — Gwen from Gavin Rossdale and Blake from Miranda Lambert.
On Monday, Gwen chatted with Carson Daly on 97.1 AMP Radio about her Halloween weekend, saying, "I was literally that party girl that you hear about when their life blows up, and you're like, 'Yeah! I'm going out! Like, watch me!' We're just trying to have fun. You know?"
This latest sighting came just days after Gwen spoke to "Extra's" Terri Seymour at the UCLA Visionary Ball about the dating rumors. Watch!