Justin Fortune began training Haumono for his Heavy weight title bout versus Joseph Parker on July 21st 2016 in New Zealand.
Haumono first took time out of rugby after his spell with the St George Illawarra Dragons in 2000. He followed in the footsteps of his father (former Australian heavyweight champion Maile Haumono) to take up a career in professional boxing. He fought eight times between 2000 and 2002, winning all of his heavyweight contests inside the distance. Solomon briefly held the title of New South Wales heavyweight champion before rejecting an offer to join the stable of American promoter Don King and returning to rugby league.
Haumono resumed his boxing career with a first round knockout on 7 March 2007. He began training under well respected trainer Johnny Lewis who has assisted Haumono in reaching his 14–0 (all by K.O) record in the heavyweight ranks]. He fought Cliff Couser on 27 August 2008 and won the fight by unanimous decision. He fought Colin Wilson on 11 March 2009 with the fight going to a draw after ten rounds. Solomon won his next fight by disqualification on 16 May 2009 against Royce Sio (1w-0l-0d). Haumono was floored in the eleventh second of the first round by a right hook from Sio, but Sio then leaned down and hit Haumono again while Haumono’s back was on the ground, leading to an instant disqualification. Haumono was back on his feet a few seconds later.
Haumono fought Justin Whitehead on 16 August 2009 and lost for the first time in his career by split decision. He defeated Michael Kirby by tenth round TKO for the OPBF Heavyweight Title on 18 September 2009, and became the Australian Heavyweight Champion after a tenth round TKO of Frankin Egobi in Melbourne on 7 September 2012.
On 31 December 2012 he fought k1 legend Kyotaro Fuijmoto under boxing rules defeating him in the fifth round via TKO.