Sania Mirza, who was gunning for her third mixed doubles Grand Slam title and second in Australian Open, and Tecau lost 3-6 2-6 against the French-Canadian duo in a 58-minute contest at the Rod Laver Arena.
The French-Canadian pair were clearly the better side in all departments of the game. Sania and Tecau, seeded sixth in the tournament, could not match up their opponents in service, return and rallies though they have lessor number of unforced errors.
Mladenovic and Nestor, who won the Wimbledon mixed doubles title last year, fended off all five break points they faced and broke the Sania-Tecau combination four times in the match.
The Indian dropped her last three service games to hand a comfortable victory to Mladenovic and Nestor.
Sania and Tecau had lost to the same opponents in the quarterfinals of the Wimbledon mixed doubles last year.
Sania had earlier won the Australian mixed doubles title with Mahesh Bhupathi in 2009.