However, the League insists the warning does not concern its variable pricing system, but rather the requirements to purchase a reserve seat.
Many membership packages require fans to pay to upgrade for fully ticketed games and the ACCC said the marketing material was likely to have created an impression there would be no additional costs.
The ACCC has put the League and some clubs on notice.
AFL.com.au understands the advertising concerned related to AFL membership and five clubs - Collingwood, Carlton, Richmond, Geelong and Hawthorn.
AFL commercial operations general manager Darren Birch told AFL.com.au, "I think one of the confusions around this is that the variable pricing strategy and the reserved seat pricing strategy came out at the same time.
"The ACCC actually haven't made any ruling on whether variable pricing is an issue," he insisted.
"The ruling is more around membership product for AFL membership and club membership.
"Clearly we have to do a better job at describing what the benefits and entitlements are of the membership product, which has got nothing to do with the pricing model related to different games at different venues at different times during the year."
ACCC chairman Rod Sims said February's variable ticketing policy announcement made existing advertising misleading, but he has only issued a warning rather than a fine.
"The reason we haven't done anything more strongly [is because] the change in policy in February meant the pre-existing ads which continued on post-February were misleading," he told AFL.com.au.
"The essential concern was that the AFL and the clubs were offering packages that you get access to a number of games when you buy your memberships," he said.
"(But) for certain games you'd have to pay more."
The League has accepted the ACCC's feedback.
The AFL removed all fully reserved classified games from round 15 onwards.
The ACCC said it would closely monitor the issue in the future.
