A woman, 26, is fighting for life, according to local media, and a man, 34, is in a serious condition.
The couple fell from a wall between two restaurants in Dubrovnik in the early hours of Saturday morning.
They lost their balance when the woman leant against the man.
The man has had surgery and the woman is in intensive care, according to reports.
“We are constantly monitoring her and doing everything we can to fight for her life,” he said.
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She said the man had a blood alcohol reading of just over 0.2, and the woman’s was 0.3.
DFAT confirmed it is is providing consular assistance to two Australians injured in Croatia.
The city is famous for being used as a location for TV show Game of Thrones and attracts millions of visitors a year.
Parts of the walls date back to the 13th century.