T-shirt and glasses, and one onlooker saw her having plenty of fun with the 'Liz and Dick' star's friend, artist Domingo Zapata.
An eyewitness told the New York Post: "Scarlett looked like she was completely flirting with Domingo."
Scarlett also hung out with actor Sam Rockwell - who arrived at the establishment following a screening for his latest movie, 'Seven Psychopaths' - but her low-key look confused many of the nightspot's revellers.
One fellow partier - whose friend had to point the blonde beauty out - said: "I didn't even recognise her."
Scarlett - who was married to Ryan Reynolds from 2008 to 2011 - appeared to be having plenty of fun without her advertising executive boyfriend Nate Naylor to the nightspot.
However, she admitted earlier this year she is in a "great" place thanks to the hunk.
The 'Iron Man' star previously said: "Everything's been really great right now. It's been a good time. I've had peace. Relative peace. I just want to work on things that are really hard, and when I'm not working on things that are really hard, I want to hang out with people I like to be with, and that's it. I think it will be an interesting year."