Kennedy was a member of the Australian U20
4 x 100 metres relay team which broke the 12-year-old Australian U20 relay record in 2022 in a time of 39.30 seconds. He represented Australia at the
2022 World Athletics U20 Championships in
Cali, Colombia. Kennedy was a member of Australia's 4x100-metre men's relay team that set a new
Oceania record of 38.12 seconds at the
2024 Summer Olympic Games. On 25 January 2025, in
Canberra, he equalled the Australian record for
60 metres running a time of 6.52 seconds, and then, later in the day, ran 6.43 seconds (+1.6) to set new
senior Australian and Oceania records and equal the tenth fastest recorded time ever. On 26 January 2025 Kennedy set a new 100m PB with 10.17 s running into a -1.0 m/s wind. At the Australian short-track championships, held in
Sydney in February 2025, Kennedy won the 60 metres with a time of 6.51 seconds. On 1 March 2025, he ran 10.03 seconds (+1.1) to win the Perth Classic 100m, moving to equal third on the Australian all-time list alongside
Matt Shirvington. He represented Australia in the 60 metres event at the
2025 World Athletics Indoor Championships held on 21 March in
Nanjing, China. He qualified for the semi-finals with a run of 6.52 seconds. After qualifying for the final, he ran 6.50 seconds to win the silver medal, one hundredth of a second behind the winner,
Jeremiah Azu of Great Britain. He won the 200 metres race at the
Maurie Plant Meet in Melbourne on 29 March 2025 ahead of compatriot
Gout Gout, running a personal best 20.26 seconds. He lowered his personal best to 10.00 seconds for the 100 metres during the heats of the Australian Athletics Championships in Perth on 11 April 2025. He finished runner-up in the final in a time of 10.01 seconds, five thousandths of a second behind winner
Rohan Browning, who was also credited with 10.01. He finished fifth in the 100 metres in 10.18 seconds at the
2025 Xiamen Diamond League event in China, in April 2025. He competed for Australia at the
2025 World Athletics Relays in China, helping the Australian men's team qualify for the 2025 World Championships. He ran a new personal best of 9.98 seconds to win the 100 metres at the
Kip Keino Classic in Nairobi on 31 May 2025. Having had the second half of 2025 ruled out by injury, Kennedy returned to competitive action with a win over 200 metres in February 2026 at the Hobart Track Classic, running a meet record 20.43 seconds (+0.6). Kennedy also set a meet record winning the 100 m in 10.03 seconds (+0.3) at the Maurie Plant Meet in Melbourne on 28 March 2026, surpassing the previous record set by
Asafa Powell in 2008. Kennedy returned later to win in rainy conditions the 200 metres at the meeting in 20.38 (-0.7) ahead of Gout Gout. On 10 April, in the heats of the 2026 Australian Championships in Sydney, Kennedy improved his personal best and became the first Australian 100m sprinter to break the 10-second barrier on home soil with a legal-wind, running 9.96 (+0.2). He ran 9.96 (+0.5) again to win the final the following day. Competing at the
2026 World Athletics Relays in Botswana the following month, he ran alongside
Joshua Azzopardi,
Christopher Ius and Rohan Browning and equalled the Oceania record of 37.87 seconds on the opening day, before placing fourth in 38.00 in the final.{{Cite web | url= https://worldathletics.org/competitions/world-athletics-relays/gaborone26/news/report/gaborone-26-report-4x100m-heats ==Personal life==