The tragic incident occurred at the firefront at Coles, near Lucindale, where the blaze is running uncontrolled through bluegum plantations, scrub and grassland, a Country Fire Service spokeswoman confirmed.
The injured firefighter has been rushed to hospital. His condition is unknown.
More than 150 firefighters are monitoring the bushfire, which has been burning for several days but is not considered an immediate threat to lives or homes.
An emergency warning was issued at one stage on Thursday night, when the fire broke through containment lines, but that was downgraded on Friday to an advice message.
About 2000 hectares have been destroyed so far.
SA CFA crews on the ground are being supported by crews from Victoria along with forest industry units and local farmers.
Water bombing aircraft have also been deployed.
"Crews will continue working along the fires' perimeter and to actively fight any areas that may flare up due to the daytime weather forecast," the CFS said.
"Whilst overnight conditions eased slightly, an increase in temperature and wind today is expected, which could hinder the efforts of crews on the ground."
The CFS said locals should stay vigilant and monitor conditions throughout the next few days as it was expected that the conditions will continuously change.
18°C