Amini played for Blacktown City before being signed to an AIS scholarship. He was signed by the Central Coast Mariners on a two-year contract in the A-League. Amini made his debut for the senior team in a friendly against fellow Gosford club Central Coast Lightning which the Mariners won 7–1. Amini made his official A-League debut for the Mariners in a match against Brisbane Roar on 20 October 2010. His first goal came in a 3–1 away win against Gold Coast United on 9 February 2011. Amini's excellent form throughout the 2010–11 A-League season attracted major interest from overseas clubs Borussia Dortmund and Bayern Munich. Subsequently it was announced that Amini was to spend two weeks on trial with Borussia Dortmund in preparation for the 2011 FIFA U-20 World Cup in July with a view of signing a long term deal with the Bundesliga club. Only days into his trial Borussia Dortmund publicly announced that the youngster had caught the eye of first team manager Jürgen Klopp stating that "he can definitely play football and is a really great talent."
Borussia Dortmund
On 4 July 2011, it was announced that he had signed with Bundesliga club Borussia Dortmund on a four-year contract. However, Amini would initially be loaned to Central Coast Mariners until 31 May 2012, making him eligible to play for the club during the 2011–12 A-League season as well as the group stage of the Asian Champions League. He played outstandingly well as Central Coast marched to the quarter-finals. On 11 July 2012, Amini made his debut for Borussia Dortmund in a friendly against SV Meppen, scoring a goal in the 63rd minute en route a 2–1 victory for Dortmund. Amini scored his first goal for the second team in a game against MSV Duisburg on matchday 7 of the 2013–14 3. Liga season. In March 2015, Amini announced, that he would leave the club when his contract expired in June, after playing there in three years.
Randers FC
Amini signed a three-year deal with Danish Superliga club Randers FC in June 2015. He scored the opening goal in the club's 3–0 UEFA Europa League qualifying second leg win over Sant Julià.
AGF
In June 2016, Amini moved to Superliga side AGF on a four-year deal. Amini enjoyed a good debut for AGF, with a goal and an assist in a 2–1 win away at SønderjyskE in the Superliga on 17 July 2016.
International career
Youth
Amini was first selected for Australia under-17 to play Turkey in a two-match series in April 2009 in Turkey. He made his Joeys debut in the first match of the series, a 1–0 loss, starting the match as a defender, but moving into midfield in the second half before being substituted late in the game. He also played a full match in the second leg, a 2–1 defeat. Amini was selected to play for Australia U-20 in a four-match tour of South America against the Argentina U-20 and Paraguay U-20 teams from 3–19 April. He was then selected for the Australia U-20 again for the 2010 AFF U-19 Youth Championship. Amini scored his first goal for the Australia U-20 in the 2010AFF U-19 Youth Championship in a 4–1 win over Vietnam U-20.
Senior
On 23 March 2011, after impressing on trial at Borussia Dortmund, Amini was called up to the Australian national side training camp by Head Coach Holger Osieck which was being held in Germany. Amini was named among the 43 players squad to represent Afghanistan for 2014 AFC Challenge Cup preparations camp in Qatar, but he refused the call saying "I only want to play for Australia if I get the chance”. Amini was called-up to Australia's senior squad ahead of the World Cup qualifiers in March 2017. He debuted on 28 March 2017 against the United Arab Emirates at Allianz Stadium in Sydney, when subbed on in the 87th minute. 20 November 2018, Amini made his first starting appearance for Australia at Stadium Australia, Sydney in a friendly match against Lebanon in front of a crowd of 33,268 people. Amini played 74 minutes before being replaced by debutant James Jeggo with Australia three goals in the lead at the time. Australia went on to win the match three goals to nil.
