Federer partnered Belinda Bencic to a 4-2 4-3 victory over Serena Williams and Frances Tiafoe in Australia.
The Swiss duo were comfortable winners in the end, adding their USA scalp to the victory over Great Britain earlier this week.
But Federer did not escape unscathed from the match.
In a freak incident midway through proceedings, Federer was struck in the face with a volley from Tiafoe.
The 20-time Grand Slam champion had dropped a shot at the net but Tiafoe struck back with a back-hand that sailed off Federer’s head.
The crowd were initially shocked and watched on as Federer grabbed his face.
But there were quickly handshakes all round as the 37-year-old seemed unhurt.
Roger Federer (20) and Serena Williams (23) are the two players with the most Grand Slams currently on the tennis circuit.
They had never previously met on court before and it was the Swiss maestro who got the win here.
Both tennis stars are expected to make an impact at the Australian Open later this month.
Federer won the men’s singles title last year, while Williams was most recently a champion in Melbourne back in 2017.
After the match Williams said: “It was a great experience. I’m kind of sad it is over; I was just warming up.
“It was such fun, we grew up together. Having an opportunity after all these years. We’ve never done that.
“It was super cool that we get to do it in the pinnacle of our careers.
“I wanted to take pictures and bring my baby out. I was way too excited.”