Romance rumors between the two surfaced after they collaborated on their new song, 'Boyfriend.'
Ariana Grande is enjoying her time with Mikey Foster.
ET has learned that the 26-year-old singer has been spending time in Chicago with her rumored new boyfriend. According to a source, Grande threw a surprise birthday party for one of her bodyguards on Sunday night following her performance at Lollapalooza, and Foster was in attendance.
"They sat next to each other during the dinner," says the source.
The source adds that the birthday bash went down in the city’s North River neighborhood at Top Chef alum Fabio Viviani's Italian restaurant, Siena Tavern. ET's source says the group was in a private dining room that was decked out in birthday swag requested by Grande herself.
"She asked for the room to include 'Happy Birthday' balloons and other decorations, as well as a special birthday cake created by the restaurant," the source notes, adding that the group sipped on Veuve and Casamigos cocktails and Grande made sure that her favorite dish at the restaurant, burrata, was served at the party.
According to the source, Grande and her rumored new beau returned to Siena Tavern on Monday and were seen holding hands at one point during the evening. The source shares that the couple arrived and left from the restaurant separately. The singer's mom, Joan, and a few other friends joined Grande and Foster at the restaurant, the source adds.
Romance rumors first circulated after Foster, as well as Scootie Anderson of Social House, collaborated on "Boyfriend" with Grande. The trio dropped the song and accompanying music video last week, and performed it during day four of Lollapalooza.
On Monday, Grande posted a selfie with her and Foster on her Insta, simply captioning it with a heart emoji, "♡."
The former Nickelodeon star also posted a video of him holding her dog. "Why does he love u this much it's weird," Grande captioned the snippet.
For more on Grande and Foster's new song, watch below.
Ariana Grande Says 'Uplifting' New Song 'Boyfriend' Is About Love, Trust and Fear of Commitment