The 24-year-old singer is rumoured to have struck up a relationship with the 'American Horror Story' actor, after pictures obtained by DailyMail.com showed them holding hands whilst enjoying a date at Six Flags Magic Mountain theme park in Los Angeles.
The images are said to have been taken last week, and a source told DailyMailTV that 32-year-old Evan - who split with his former fiancée Emma Roberts in March - appeared to be ''flirting'' with Halsey as they lined up for the Goliath rollercoaster.
The onlooker said: ''They were laughing and flirting the whole time while we waited for the ride, it looked really romantic. It looked like they were having a fun date night before the Emmys. We were so surprised, because we didn't even know that they knew each other. They were smiling and laughing together and looking into each other's eyes as they were waiting for the ride to start. When we got off the roller coaster, we bought the photo of them on the ride and saw that they were holding hands, their fingers were intertwined.''
Halsey had previously been in a relationship with fellow singer Yungblud, and although there has been no news of their split, the 22-year-old musician seemingly hit out at the situation on Instagram shortly after the pictures were published.
In a video, Yungblud asked for his own date to a theme park similar to Halsey's, as he said: ''Somebody take me to Disneyland.''
Meanwhile, the 'Nightmare' singer also dated rapper G-Eazy for nine months before calling it quits last year, and recently described the split as ''heinous''.
Halsey explained she realised she had to continue being herself despite her hardships when confronted by two ''brave'' fans in the wake of her break up.
She said: ''I was doing 'Good Morning America' and I'm in a blonde wig and white patent-leather outfit, twirling around while I'm going through a heinous breakup. I look down and there are these two girls, one with pink hair, one with blue hair, septum piercings, cool as f**k, still loving me, probably knowing what a weird time I'm going through.
''[I] went, 'Ohhh no, they deserve way better than this.' If those girls can be that brave in who they are, then I owe them better than this homogenised bulls**t.
''But hey, if the worst thing that's happened to me so far is I wore dumb clothes and dated a s**tty dude, I think I'm doing all right.''