Katie Holmes surprised everyone when she appeared at an event hosted by her secret boyfriend, Jamie Foxx.

Her surprise appearance happened during the opening of the Privé Revaux Eyewear's flagship store in New York on Monday. The event was co-hosted by Foxx. According to an insider, the actress showed up unannounced, to the surprise of the other guests.

"Katie came toward the end of the event," said the source. "No one knew she was coming."

Holmes looked gorgeous in a simple satin black dress black heels and long pink coat with yellow flowers as buttons. Foxx, on the other hand, wore a black shirt and jeans and rocked a gray peacoat.

Other notable guests at the event include New York Giants athlete Odell Beckham Jr., New York Mets pitcher Brandon Nimmo, actress Margot Bingham and rapper Nicki Minaj.

Foxx, who was working the DJ booth at the time of Holmes' arrival, took a break to hang out with her backstage. After hanging out for a while, the two left the event separately. Reports also said that Holmes bought 13 pairs of sunglasses at the boutique.

Foxx and Holmes have been quietly dating for four years. The couple only went public about their relationship during Labor Day weekend earlier this year. They were seen holding each other's hands at a beach in Malibu. The two enjoyed the end of summer, sharing a romantic stroll at the beach before having a splash in the waves.

The very private couple has been rumored to be together since 2013, but they did not publicly confirm their relationship until recently.

"Everyone knows they're together, but it's still unspoken," said a source. "He could often be overheard talking flirtatiously to someone on the phone and excited to wrap up work and go home. It's been obvious that he's had someone special in his life for a long time."