In 1999 at the age of 23, Graham won the Amateur Australian and New Zealand Open Weight Championships and soon also became the South Pacific Champion.

However, Graham only completed three months of this rigorous training before having to return to Australia after his brother Matthew died of a heroin overdose.

Graham turned professional in 2000 and attained instant success, defeating Ben Hamilton in K-1 Oceania Revenge by TKO and then Clay Aumitagi.

!, Graham fought against the four time K-1 heavyweight champion, Dutch man from the Seidokaikan dojo Semmy Schilt in a 5-round match and lost by unanimous decision (3–0).

[6] In a rematch with Doug Viney at Kings of Kombat in Keysborough, Victoria on 29 August 2010, Graham won via TKO in the fifth round to claim the ISKA World Heavyweight Championship.

He is competed in a Heavyweight Tournament at GFC Series 1 in Dubai on 29 May 2014, defeating Arnold Oborotov via an extension round majority decision in the semi-finals before losing to Badr Hari by first-round TKO in the final.

[14] Graham was scheduled to fight upcoming MMM star Tai Tuivasa in Combat8 at C8:03,[15] a Mixed Rules Australian MMA organization.

Graham defeated Tai Tuivasa[16][17] by TKO in the second round in a back and forth fight, making that his eighth KO/TKO MMA win so far.

[24] Peter Graham grew up in Sydney NSW Australia he was a street kid that lived in youth refuges till he was 20.

After the tragic heroin overdose of his older brother he returned to Australia to bury him and start his journey back to Japan and to K1 kickboxing greatest heights.

Five years later he won the amateur kickboxing world titles undefeated and turning pro he returned to Japan to fight K1 and eventually to married a Brazilian woman living in Tokyo on 22 June 2008.

[29] They have two daughters together, and in 2010, Graham appeared on the TV program "Find My Family" where he was re-united with his younger brother who he had lost contact with and hadn't seen in 20 years.