The tennis legend and his family became the latest high-profile stars to watch the Eras Tour live after they were spotted soaking up the action at Stadion Letzigrund.
The Swiss 20-time singles major tournament winner also posted a photo to his Instagram of him collecting friendship bracelets at the concert.
Federer’s bracelets could be seen sporting the words ‘Problems’, ‘Hero’, and ‘Wildest’, in likely references to the Swift songs ‘Champagne Problems’, ‘Anti-Hero’, and ‘Wildest Dreams’.
Federer also appeared to have access to the ‘Fearless Lounge’ part of Swift’s concert.
Federer’s appearance at one of Swift’s shows in his home country comes less than a month after the ‘Blank Space’ singer left female tennis star Iga Swiatek a handwritten note after one of her Liverpool shows.
Swiatek showed the note on social media soon after and revealed she was in tears upon receiving it.
Swift is playing two shows in Zurich before two shows in Milan this weekend.
Swift’s worldwide tour concludes with shows in Canada in November and December.
The 14-time Grammy winner will continue to tour Europe for the next month, concluding with more shows at London’s Wembley Stadium.
Federer retired from tennis in 2022 as one of the most successful athletes in the sport’s history, having long-standing rivalries with Rafael Nadal and Novak Djokovic.
Travis Kelce was joined by his retired NFL brother Jason Kelce during Swift’s first block of London shows last month, with several of their family members also making the trek across the pond.