The Canberra League consisted of Ainslie, Belconnen, Eastlake, Manuka-Weston, Queanbeyan and Tuggeranong. Ainslie played their home games at the redeveloped O’Connor Oval.
In the last home and away game Ainslie defeated Eastlake by 163 points with full forward Chris Fleming kicking 15 goals. Ainslie finished the home and away in second place with 15 wins, 3 losses and a draw behind Queanbeyan with 18 wins.
Ainslie played top team Queanbeyan in the Second Semi-Final at Football Park. Ainslie had a dominant first half leading by 6 goals at the long break. They went on to win by 29 points and advance through to the Grand Final.
- Final score: Ainslie 23.13-151 def Queanbeyan 19.8-122
- Goal kickers for Ainslie: Fleming 7, Mohrwinkel 5, Sinclair 2, Zochling 2, McTaggart 2, Conway 1, Hannam 1, Baxter 1, Ireland 1, A Bishop 1
- Best: Sinclair, Mohrwinkel, Hannam, Fleming, Conway, McTaggart, Bishop
Ainslie played Queanbeyan again in the Grand Final at Football Park. In a hard fought, fiery match Ainslie ran out winners by 27 points to win their 16th Premiership.
- Final score: Ainslie 16.12-108 def Queanbeyan 10.21-81
- Goal Kickers for Ainslie: Hannam 4, Fleming 4, Mohrwinkel 3, Hird 2, Conway 1, Kelly 1, Foley 1
- Best: Hannam, Bishop, Muir, Conway, Killer, Kelly, Foley
The Ainslie Team for the Grand Final was:
- Backs: Jamie Dennis, Mark Killer, Ian Muir
- Half Backs: Peter Brown, Maurice Wingate, Scott Gibson
- Centres: Andrew Bishop, Matt Conway, Robert Kelly
- Hal Forwards: Mark Sinclair, Brett Hannam, James Hird
- Forwards: Jeff Mohrwinkel, Chris Fleming, Gerard Zochling
- Rucks: Barry Denton, Jack Ireland, Robbie Baxter
- Bench: From Michael Richardson, Shane Stockwell, Stephen Kent, Peter Foley
Other players who played in First Grade during the 1990 season were:
Greg Bishop, Grant Brady, Michael Collins, David Graham, Darren Hawkins, Gordon Marshall, John Read, Luke Revet, Pas Rocca, Wayne Rogers, Craig Smith, Brenton Walters
Chris Fleming led the Ainslie First Grade goal kicking with 62 goals in only 8 games.
Ainslie won the C.W. Chandler Trophy for the Club Championship.Captain/Coach Brett Hannam won the FM104.7 Player of the Year Award.
Ainslie players that played for the ACT Representative team were:
Barry Denton, Brett Hannam, James Hird, Andrew Bishop, Ian Muir, Maurice Wingate, Peter Ireland, Michael Richardson and Jeff Mohrwinkel.
James Hird at age 17 was drafted by Essendon at pick 79 and went on to play 253 AFL games. Hird had played 7 First Grade games with Ainslie in 1990 including the Grand Final.
Chris Smith, an ex-Ainslie Junior, also aged 17 was drafted by Richmond at pick 28 but did not play an AFL game. Returned to Ainslie in 1999 and played 27 First Grade games.