The offseason and preseason saw the signings of Fábio Ferreira from Sydney-based Dulwich Hill FC, Marcelo Carrusca, Daniel Bowles and Jake Barker-Daish.

The club's home and away season began away to Newcastle Jets on 7 October 2012 just four days after being eliminated from the 2012 Asian Champions League.

Adelaide United responded to the loss in kind the following round at home, coming from a goal down to defeat Wellington Phoenix 3–1 in Cássio's 100th A-League match.

Adelaide successfully defended the lead and won the match 1–0, with much notable praise heaped on goalkeeper and captain Eugene Galekovic.

Vidosic struck home the winner in the 88th minute, Adelaide winning 2–1 and continuing Sydney FC's poor form.

Eugene Galekovic and Dario Vidosic had been selected to compete for Australia in the East Asian Cup, and therefore did not play the match.

Paul Izzo made his debut in place of Eugene Galekovic, becoming the 100th-ever player to make an appearance for Adelaide United.

The match indirectly attracted controversy when reports surfaced of apparent massive, multimillion-dollar bets being placed on the game.

Evan Kostopoulos scored his first ever A-League goals, netting a brace, with Ferriera and Carrusca adding to Adelaide's tally.

Carrusca scored an astonishing effort, striking the ball with his first touch on the right flank it curved to the inside left of the goal, around Melbourne Victory goalkeeper Nathan Coe.

A week later Adelaide notched an eighth win for the season, again defeating Wellington Phoenix 3–1, with a brace to Carrusca and a goal by Ferreira.

Cameron Watson, Bruce Djite, Cassio, Jeronimo Neumann and Fabio Ferreira each extended their contracts for a further two years.

Both supporter groups staged a silent protest, with the issue being given significant media attention on internet and radio, citing disconnect with the club and heavy-handedness by security staff.

Valkanis' first match in charge saw Adelaide lose 2–4 at home to Western Sydney, but a week later delivered a resounding 1–0 win over Melbourne Victory, Jeronimo Neumann once more the lone goalscorer.

The triumph ended Victory's run of form, who subsequently struggled for positive results for the remainder of the season.

It was announced on 1 December 2011 that as part of the AFC Champions League review conducted earlier in the year, Australia would be granted an extra play-off slot for the 2012 edition of the competition.

On 29 August, the club announced a one-year front-of-shirt sponsorship partnership with Unleash Solar[11] worth a reported $250,000.