He played two seasons of college basketball in the United States for the California Baptist Lancers before joining the Taipans in 2023.
Growing up in Burnie, Tasmania, Armstrong was exposed to basketball at an early age due to his father, Ben, playing semi-professionally for the Wynyard Wildcats in the North West Basketball Union (NWBU) along with his uncle, Ben's brother Sam.
[3] He played in the NWBU for Burnie and Wynyard[4] before moving to Canberra in mid 2018 after being awarded an NBA Global Academy scholarship with Basketball Australia's Centre of Excellence.
[6] He also helped Tasmania claim a bronze medal at the 2020 Under 20 National Championships after averaging 25 points per game.
[10] He recorded the program's first triple-double with 16 points, 12 assists and 10 rebounds against San Jose State on 18 November; had a career-high 11 rebounds against San Diego Christian on 27 November; broke the program record for single-game assists with 15 against North Dakota on 7 December; and scored a season-high 22 points against Utah Valley on 26 February.
[14][15] On 17 May 2023, Armstrong signed a two-year contract with the Cairns Taipans of the National Basketball League (NBL).
[23][24] In 2019, Armstrong represented Australia at the FIBA Under-17 Oceania Championship, where he helped his country win the gold medal with 11 points per game.