From 1963 to 1976 Margarita Shtarkelova played basketball for Lokomotiv Sofia, winning the Bulgarian league in 1967, followed by the Bulgarian Cup a year later. With the team Shtarkelova also finished as a runner-up in the league in 1971, in addition to placing third on six occasions. During her career she was also a mainstay in the Bulgarian national team, winning silver and bronze at the European Championships in 1972 and 1976, respectively.
Bulgaria dominated the Balkan Cup in the late 1960s and early 1970s, with Shtarkelova being on the gold medal winning team on six occasions (1969–70, 1972–75). In 1976 she also won bronze at the Montréal Olympics, playing in all five matches and scoring 36 points. At the end of the 1970s Shtarkelova had a brief stint playing for Basket Puglia in Italy, before returning to Bulgaria to finish her playing career. Her son Martin was a successful volleyball player and coach.
Bulgaria