League chairman Mike Fitzpatrick announced to no-one's surprise on Wednesday that McLachlan would succeed Andrew Demetriou as chief executive.
Demetriou's last day in charge will be on June 5.
McLachlan takes over the running of Australia's biggest and most powerful professional sporting organisation, but also a body facing significant challenges.
The game is nervously awaiting the outcome of ASADA's investigation into the Essendon supplements scandal, with McLachlan not expecting a verdict until late this month.
Demetriou hopes to achieve some agreement on the thorny issue of club equalisation by the time he leaves but Fitzpatrick admits there is no guarantee that will happen.
McLachlan said he would not try to emulate Demetriou's style but said there would be no sudden change.
"I will be a different leader to Andrew - there's only one Andrew," he said.
"It will mean I take a different approach.
"The shape and structure of the team will change but it's essentially consolidating and extending the work that's happened under Andrew's tenure."
McLachlan and Fitzpatrick acknowledged that the AFL must address growing unrest among fans about the costs of going to a game.
The AFL has worn considerable flak so far this season about its new variable pricing structure for tickets.
There are also perennial complaints about the cost of food and drinks in stadiums.
"We hear the fans around the total cost of going to a game," McLachlan said.
"We will be addressing the cost of going to the football.
"Cost is more than just ticketing - it's ticketing charges; it's food and beverages."
Fitzpatrick added they would continue with the variable pricing system.
"The assessment would be we haven't done the communications particularly well on that," he said. AAP