The Melbourne native has spent the last three years at Ingolstadt and played 30 times this season as his side failed to avoid relegation from the top flight.
Hertha confirmed on Monday that Leckie would be making a move to the German capital in time for next season’s Bundesliga and Europa League campaign.
“At 26 years old he is a seasoned Bundesliga professional,” Hertha sporting director Michael Preetz said.
“His experience can help us with the demands of the coming season.”
Leckie, who can play on both wings or as a central striker, has been playing in Germany since 2011. Before helping Ingolstadt win the Bundesliga 2 title in 2015, he played for Borussia Mönchengladbach and spent time on loan at FSV Frankfurt.
At international level, Leckie was part of Australia’s World Cup squad in 2014 and helped them win the Asian Cup a year later. He will link up with Hertha after representing his country at next month’s Confederations Cup in Russia.