The 70-year-old will take charge of pre-season after having a tumour removed from his bladder, the Sun on Sunday has reported.
Tests later showed that the tumour was not malignant, but Redknapp will have further check-ups every three months.
"I could feel it in my body - I knew it wasn't right. This is the first time I've been properly worried," he said.
Redknapp took charge of the Championship club in April after Gianfranco Zola resigned, and succeeded in saving them from relegation.
The former West Ham and Tottenham boss signed a one-year contract with Birmingham the following month.
He told the paper that it was his wife Sandra who urged him to seek medical advice.
"They cut it out, took it away, sent it away to make sure it is not malignant and luckily everything was OK. I know I am fortunate," Redknapp said.
"They cut it out, there was no other option. Once they did that I was up and about after a couple of days. I am relaxed about it now because what can you do?"
Redknapp and the Birmingham squad arrived in Austria on Sunday for a pre-season trip that will see them play friendly matches against German club Union Berlin and Hapoel Ironi Kiryat Shmona from Israel.
Birmingham City boss Harry Redknapp has been given the all-clear by doctors after emergency cancer surgery.