Qadir has previously represented Perth Scorchers in the tournament; he joins as cover for Tanveer Sangha, who is recovering from a back problem
Pakistan leg-spinner Usman Qadir is returning to the Big Bash after joining Sydney Thunder.
Qadir, 29, has been recruited as cover for Tanveer Sangha, who is recovering from a stress fracture that has stunted the start to his season.
The Pakistan international has previously represented Perth Scorchers, as well as playing grade cricket in Sydney and Adelaide, at which point he was looking to represent Australia.
"Usman joins us with plenty of experience, having represented Pakistan, and playing in T20 leagues around the world," said Andrew Gilchrist, Thunder's head of cricket.
"Importantly, he has first-hand knowledge of Australian conditions, he played for Western Australia and South Australia's futures league, so he knows what to expect."
Qadir has previously played for Perth Scorchers in the Big Bash (Will Russell/Getty Images)
Qadir, who was a reserve during the recent T20 World Cup, has represented Pakistan 23 times. He had been named in his country's squad initially but was replaced by Fakhar Zaman after suffering an injury.
He is Sydney's fourth overseas signing, following Alex Hales, Rilee Rossouw and Fazalhaq Farooqi. Farooqi, the Afghanistan seamer, replaced David Willey after the Englishman pulled out.