The spotting comes after the rumored couple was seen together at a swanky London hotel.
A source tells ET, "Irina and Tom have a good thing going. It's light and fun between them and they are super attracted to each other."
The source adds that the seven-time Super Bowl champion and the Russian model "bond over the fact that they're hardworking and dedicated parents" and "Irina is Tom's type, and she enjoys being around him."
The pair has been frequently spotted in each other's company, and on Tuesday, the 46-year-old retired athlete and the 37-year-old model were seen at his Tribeca apartment.
An eyewitness tells ET that after attending the Michael Kors fashion show, Shayk was the first to arrive at Brady's apartment around 11 a.m., but stayed in her chauffeured SUV for about 20 minutes. Once the former NFL star arrived and entered the building, Shayk followed suit a few minutes later.
"She waited and did not go in with him," the eyewitness adds. "They are definitely trying to be discreet and not be seen together." ET is told the couple spent the rest of the afternoon holed up inside his place.
Early last month, Brady and Shayk took their rumored romance global and were spotted at a swanky London hotel, with a source telling ET that they went to "great lengths to not be seen together." Brady arrived at The Twenty Two hotel after attending the Birmingham City match against Leeds United. The following morning, Shayk was seen exiting the same hotel, though she appeared to be keeping a low profile.
Brady and Shayk were seen leaving the hotel just two days later and five minutes apart, using separate exits. A source told ET that the pair barely left their room and ordered room service to avoid being seen.
"They were trying to keep their stay top secret... They didn’t go anywhere together and were using different exits at the hotel," the source said. "It was all carefully orchestrated. They definitely seemed keen to keep their romance under wraps as much as possible."
The pair seem to be skillfully juggling their blossoming relationship and co-parenting with their respective exes.
Shayk and her former flame, Bradley Cooper, with whom she shares a 6-year-old daughter, Lea, are particularly friendly exes. The pair, whose relationship came to an end in 2019, seemingly vacationed together last month, which Shayk revealed on her Instagram Story.
Amid photos of the model enjoying the cloudless sky and idyllic scenery, she shared a snapshot of the 48-year-old A Star Is Born actor lying in a kayak on the water, holding his hand above his eyes to block out the sun, in what appears to be the same location as Shayk.
As for how Brady's ex-wife, Gisele Bündchen, is handling Brady and Shayk's burgeoning romance, the source previously told ET that the Brazilian supermodel "isn't thinking about what Tom is doing in his romantic life" and, instead, "she's focused on their children, co-parenting, and maintaining a good environment for everyone."
Brady and Bündchen share two children -- Benjamin, 13, and Vivian, 11. Brady also shares a 16-year-old son, Jack, with his ex, Bridget Moynahan.
Furthermore, the source said "Gisele's main priority is to make sure their kids feel loved and cared for. She wants to set a positive example for them and Gisele is doing her own thing."