[5] Harrington won the 2020 European Boxing Olympic Qualification Tournament, by defeating Caroline Dubois on a split decision in the final.

[10][11][12] In her final on 8 August, Harrington defeated Beatriz Ferreira 5–0, winning the gold medal and becoming Ireland's third Olympic boxing champion.

[14][15] Harrington won gold at the 2023 European Games in Poland, defeating Natalia Shadrina from Serbia in the final by unanimous decision.

[32] Harrington was joint grand marshal with Ellen Keane at the Dublin St Patrick's Day parade on 17 March 2022.

[36] She has stated that she intends to return to her part-time cleaning job at St Vincent's Psychiatric Hospital in Dublin, regardless of her result at the Olympics.

[41] On 2 April 2023, Harrington announced her withdrawal from social media following a backlash as a result of a tweet from GB News relating to immigration, which she shared and subsequently deleted.