Sandu spent his entire playing career in Romania, most notably with the FC Sportul Studențesc București, becoming one of the club's most prolific goal scorers.
[3] The following season he went to play for Sportul Studențesc București in Divizia B where he scored 15 goals in 28 matches, helping the team earn the promotion to the first league.
[3] In the following 14 seasons, Sandu played for The Students in Divizia A, the highlights of this period being 21 goals scored in the 1975–76 season, helping the team earn a second position in the 1985–86 season, being introduced at halftime to replace Ion Munteanu by coach Mircea Rădulescu in the 3–0 loss in front of Steaua București from the 1979 Cupa României final and representing the club in 6 UEFA Cup matches in which he scored two goals, including one against goalkeeper Walter Zenga in a 1–0 victory against Inter Milan, also helping the team win the 1979–80 Balkans Cup and reach the final in the 1976 edition.
[3][5][6][7][8] After his period spent at Sportul Studențesc, Sandu went to play for Gloria Buzău for one season, making his last Divizia A appearance on 21 September 1987 in a 1–0 victory against Universitatea Cluj in which he scored the goal.
[10][11] Mircea Sandu made 16 appearances and scored 4 goals at international level for Romania, making his debut on 8 April 1972 when coach Angelo Niculescu used him in a friendly which ended with a 2–0 victory against France.