The 36-year-old Miller missed Paarl Royals' playoff matches and was ruled out of the Proteas T20I series against the West Indies.
A statement from the Proteas camp said the left-handed batter has been "medically cleared" to take part in the T20 World Cup that kicks off on 7 February.
The news will welcomed as Miller is the Proteas most experienced player, having played 133 T20Is, scoring 2630 runs at an average of 32.87 and a strike rate of 140.56.
The Proteas had already suffered two injury setbacks ahead of the global tournament after Donovan Ferreira and Tony de Zorzi were ruled out after the squad was named.
Ryan Rickelton and Tristan Stubbs were named as replacements and have been with the team that have won the home series against the Windies.
The Proteas will depart for Mumbai on Sunday and take on co-hosts India in a warm-up game on Wednesday.
Shukri Conrad's charges will open their T20 World Cup campaign against Canada in Ahmedabad on 9 February, before further group fixtures against Afghanistan, New Zealand and UAE.
Sri Lanka have confirmed their 15-man squad for the ICC Men's T20 World Cup 2026, backing experience at the top while making decisive calls in the middle order ahead of the tournament's start this weekend.
Josh Hazlewood is set to miss the start of Australia's T20 World Cup campaign after remaining at home to continue his rehabilitation from his Achilles injury.
The ICC has warned the Pakistan Cricket Board of "long-term implications for cricket in its own country" if the national team boycott's the game against India at the T20 World Cup.
Quinton de Kock praised Ryan Rickleton's ability to adjust to the No 3 role and believes the rest of the lineup will need to show similar levels of adaptability if the Proteas are to win the T20 World Cup in India.
