Gabriella Mészáros started her sports career in 1926. As a gymnast with OTE she won the team championship in the second division and finished fourth in the individual all-around. In the same year she moved to BBTE (Budapesti Budai Torna Egylet) and won a national team championship in 1934, which she repeated three more times (1935, 1937-38). In 1935, 1937, and 1938 Mészáros was Hungarian individual all-around champion and won a total of 12 apparatus titles. From 1934-36 she was on the Hungarian national team. Mészáros finished second at the 1934 World Championships and third at the 1936 Berlin Olympics in the team events. In 1944, after her son was born, Mészáros ended her active sports career.
After graduating from high school, Mészáros was an intern and then an assistant officer at the Royal Hungarian Postal Savings Bank. Starting in 1949 she became the head coach of the gymnasts of the Egyesült Izzo and Újpesti Dózsa, but in 1954 she quit coaching to raise her children. From 1959 until her retirement, she was treasurer of the National Savings Bank.