Cricket South Africa confirmed on Monday that the 31-year-old will miss the tournament in Windhoek, where the Proteas face hosts Namibia and Zimbabwe from August 28 to September 6. Smith will undergo further assessments to determine whether he will be fit for the three-match ODI series against Namibia, which begins on September 9.
The Proteas have chosen not to name a replacement, leaving the squad unchanged ahead of its departure for Windhoek on Tuesday.
Smith's absence removes one of the more experienced players from an otherwise youthful white-ball squad. Having featured in South Africa's squad at the 2026 T20 World Cup, he has played 11 T20 Internationals and three One-Day Internationals for the Proteas.
His withdrawal could open the door for uncapped all-rounders Duan Jansen and Eathan Bosch to make their international debuts during the tri-series.
The injury is another concern for South African cricket after Kagiso Rabada suffered a hamstring strain during winter training, while Senuran Muthusamy missed the South Africa A series against Bangladesh A with a lower back spasm.
Neither Rabada nor Muthusamy were part of the touring squad for Namibia, with South Africa resting several senior players ahead of a busy home summer that includes eight Test matches.
The tri-series will be South Africa's first T20I assignment since reaching the semi-finals of the 2026 Men's T20 World Cup under Aiden Markram. Bjorn Fortuin will captain the side in Windhoek before attention shifts to the ODI series against Namibia later in September.
Pat Cummins has welcomed Australia's long-awaited return to South Africa, describing the Proteas as a "really strong side" as the visitors begin preparations for a three-Test series in October.
Proteas fast bowler Kagiso Rabada has suffered a hamstring injury while doing a winter training programme and will undergo further assessments with a home ODI series against Australia to come next month.
Temba Bavuma is "all good" and should be ready to take the field when Australia arrive on South African shores for the three-match ODI series next month, according Proteas coach Shukri Conrad.
Bjorn Fortuin has been selected as captain of the Proteas 15-man squad for the white-ball tour to Namibia, starting later this month, with Temba Bavuma (ODI) and Aiden Markram (T20I) being rested.
