Chappell was the youngest of the Chappell cricketing brothers, Ian and Greg, and the grandson of former Australian captain Vic Richardson. Chappell grew up playing cricket in the backyard with his brothers and like them was coached by Lynn Foster and attended Prince Alfred College.

Greg Chappell later recalled, "I was going to be every bit the tyrant to Trevor that Ian had been to me. But TC was his own man. Trevor was quiet and unassuming, but if you pushed him too far, he'd explode. That's TC through and through: very passive most of the time, easy going, but push him too far and there's an explosion coming."

Chappell's childhood hero was Keith Miller. Throughout his early playing career he was a batsman, although his excellent fielding at cover also brought him attention. "I figured the cover region was the area where the ball went more often than not, so I thought it was a good spot to field", he later said. "It keeps you occupied and always in the game."

Over the summer of 1969/70 he toured the West Indies with the Australian Schoolboys XI, a team that also included Gary Gilmour, Gary Cosier and Ian Davis. During the tour he came down with chicken pox. He recovered to score 52 against St Kitts.

Chappell also played for South Australia in the Australian Schoolboys Cricket Council Championships in Sydney.

1973–73

Chappell debuted for South Australia in the 1972–73 season, replacing Ken Cunningham who had to drop out because of business reasons. He later recalled:

When I first got picked for South Australia, Ian said, "You got to decide what sort of a player you want to be – whether you want to be an aggressive, attacking player, or more like a grafting sort of player." I had to think about that and that I'm not really a free hitter of the ball, so the choice I made was I was going to be more of a grafter.

His career began well, scoring 67 on debut. He made half centuries in his next two games, but struggled thereafter and was eventually dropped from the South Australian side. Chappell:

When I first played for South Australia, I did all right. Then I got injured right at the start of the second season – I broke my nose and cheekbone in a fielding accident. I damaged my shoulder as well. I couldn't throw very well. Fielding has always been one of my main skills and I lost confidence in the fielding. I wasn't getting any runs, I wasn't bowling much in those days, and I wasn't fielding terribly well either. I ended up playing all of the first-class season and had a bad season. I still couldn't get runs in South Australia the following season but I'd go to England and get runs. I got dropped from the South Australian team.

1975: League Cricket

In 1975 Chappell played for Walsden in the Lancashire League over the English summer. It was a highly