The 2012–13 Western Sydney Wanderers FC season was the club's inaugural season since its establishment in 2012. The club participated in the A-League for the first time, winning the competition and finishing as runner-up in the 2013 A-League Grand Final.

On 4 April 2012, Western Sydney Wanderers was established by FFA as a Western Sydney based club to compete in the A-League. On 17 May, Tony Popovic was announced as inaugural head coach. Popovic joined the club on a four-year deal after requesting to be released from the final year of his contracted role as assistant manager of Crystal Palace. On 22 May, Ante Milicic joined the club as assistant coach. On 25 June, the first players to sign to the new club were announced, these were Aaron Mooy from St Mirren, Tarek Elrich from Newcastle Jets !Newcastle Jets and Kwabena Appiah-Kubi from Central Coast Mariners !Central Coast Mariners. All three players signed a one-year contract, as would all players in the inaugural squad, with exception of two (Beauchamp and Ono). On 30 June, Sydney players Michael Beauchamp, Mark Bridge and Shannon Cole, as well as Nikolai Topor-Stanley from Newcastle Jets FC all signed for the club. Beauchamp was the first player to sign past the inaugural season, with a three-year contract. On 2 July, Ante Čović joined the squad from Melbourne Victory !Melbourne Victory and Labinot Haliti joined from Newcastle Jets !Newcastle Jets. On 25 July, after just two months of developing a squad, the club played its first friendly match against local club, Nepean. The game ended in a 0–5 win for Wanderers, with Haliti scoring one and Gibbs scoring four in front of a crowd of 3,500. On 31 July, Adam D'Apuzzo signed to the new club from APIA Leichhardt Tigers. On 2 August, Jerrad Tyson joined the squad from Gold Coast United, Jason Trifiro joined the squad from South Melbourne and Reece Caira joined from Aston Villa. On 8 August, Tahj Minniecon joined the squad from Gold Coast United. On 13 August, Dino Kresinger joined the squad from Cibalia and Mateo Poljak joined from Dinamo Zagreb. On 21 August, Jérome Polenz joined the squad from Union Berlin. On 11 September, Iacopo La Rocca joined the squad from Grasshoppers and Youssouf Hersi joined from Alki Larnaca. On 28 September, Japanese midfielder Shinji Ono became the club's International Marquee player, signing to the club for two years from J. League Division 1 team Shimizu S-Pulse. On 3 October, Joey Gibbs joined the squad from Marconi Stallions FC.

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