In addition to his suspended sentence, Mitchell was fined £1,094 by Brisbane magistrates.
Exeter said in a statement that they do not condone law breaking of any kind.
The statement read: "Exeter Rugby Club deeply regrets that one of its employees has faced court action in relation to their personal behaviour.
"The club does not condone law breaking of any kind and will continue to stress with all of its employees the importance of acting as positive ambassadors - even in difficult and unwanted circumstances.
"Craig Mitchell wishes to express his remorse not only to the victim and those involved in the incident, but also to Exeter Rugby Club, the Welsh Rugby Union and his family."
Mitchell, who joined Exeter from the Ospreys in 2011, has been capped 15 times by Wales.