Michaela Walsh gained her first experience at international competitions at the European Youth Olympic Festival 2013 in Utrecht , where she finished tenth in the final. A year later she qualified for the Youth Olympic Games in Nanjing , where she reached sixth place in the shot put final with 15.69 m. In 2015 she took part in the U18 World Championships in Cali , where she was ninth in the shot put and tenth with the hammer. A year later, she finished eleventh at the U20 World Championships in Bydgoszcz, Poland, in the shot put with 14.73 m. In 2017 she took part in the U20 European Championships in Grosseto , where she won the bronze medal in hammer throw with 61.27 meters. She also reached seventh place in the shot put.
In 2017 and 2018 Walsh became Irish indoor champion in the shot put.