The 35-year-old recently penned a one-year contract with the National First Division outfit after a stint with Ladysmith United in the ABC Motsepe League.
Sibisi previously led the line at Free State Stars, Ajax Cape Town, Maritzburg United, University of Pretoria and Mpumalanga Black Aces in the Absa Premiership, while he also plied his trade for Vietnamese side Fico Tay Ninh.
"We have been playing well but always struggled in front of goals," says Uthongathi manager Nkosinathi Chili.
"Diyo is also joining Uthongathi to offer experience to the young players.
"He has signed a one-year [contract] with an option to renew," he adds of Sibsi, who last featured in the South African topflight in 2013.
Chili also confirmed Uthongathi have decided against signing ex-Golden Arrows midfielder Philani Shange. Shange had been training with the second-tier club.