Errani and Vinci, the No. 1 seeds, beat the Australians 6-2, 3-6, 6-2.
Barty and Dellacqua opened the third set with a break but the Italian team quickly rallied to take control of the set and pick up the championship.
It was the third doubles title in the last four Grand Slam tournaments for Errani and Vinci, who were the runners-up at the 2012 Australian Open, and winners at the French and U.S. opens.
Barty and Dellacqua, who had played only seven matches together before the Australian Open, opened their tournament with an upset of third-seeded Maria Kirilenko and Lisa Raymond and didn't drop a set until the finals. They were the first all-Australian team to make the women's doubles final in 35 years.