Barbro Martinsson first competed for Valbo AIF until 1957, including her first Olympic appearance in Cortina d’Ampezzo in 1956. However, she achieved most of her great successes over the years racing for Skellefteå SK. In later years she joined Timrå SOK (1971-74). Martinsson took part in three World Championships and four Olympic Games. She won two Olympic silver medals with the Swedish 3x5 km relay team in 1964 and 1968. She also won two medals in the 3x5 km relay at the World Championships, silver in 1962 and bronze in 1966. At the 1968 Winter Olympics, she finished in fourth place at both 5 and 10 km races individually, missing the bronze medal by 1.3 and 7.2 sec, respectively. At her fourth Olympics, she was the flagbearer of the Swedish team during the Opening Ceremony. In World Ski Championships she placed sixth in the 10 km in 1962 and 1966. Her greatest success individually was the victory at Holmenkollen over 10 km. At home, she won four individual Swedish Championships (two each over 5 and 10 km) and three with the Skellefteå SK relay team.
Martinsson was named Swedish Sportswoman of the Year in 1964 together with Toini Gustafsson and became “Stor Grabb” (Big Boy) No. 52, an honorary award in Swedish sports. She worked at BP Lundin, where she was often seen refueling cars. She was also a reckless rafter balancing on some logs on the Skellefte River. During the summer, she was an accomplished orienteering and track runner. In total she has won 57 district championships in different sports, including handball. She is married to former cross-country skier and Olympian Sture Grahn.