Sandhu, the first Australian of Indian origin to represent the country in cricket at the international level, won the medal with 146 votes, three clear of Haddin.
The honour has made him the first Indian and the first rookie to win the medal, ousting Haddin (143) and Trent Copeland (133) at the awards ceremony in Doltone House here.
Sandhu has, so far, played only two Sheffield Shield four-day matches and four domestic limited-overs fixtures.
Sandhu, who lives in Blacktown, was the active member of the Australia team at the 2012 Under-19 World Cup.
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He made his debut this season for the Sydney Thunder in the Twenty20 Big Bash and also featured in the Prime Minister's XI match against the West Indies. He also took four wickets in two Australia 'A' games against England 'A'.
Sandhu, whose father emigrated from Punjab 30 years ago, also won the Ryobi Cup player of the year, beating Steve Smith and Haddin.