The right-hander won one singles title (1999, Bournemouth). Voinea was born in Focsani, Romania, but moved to Italy at age 15 to train with his older brother, Marian. His brother played a crucial role in developing his career. He was his tennis coach, mentor, support system, strategist and hitting partner. Adrian reached his career-high ATP singles ranking of World No. 36 in April 1996. One year before he achieved his greatest success by advancing to the quarterfinals of the 1995 French Open as a qualifier, defeating Boris Becker in the third round in four sets. Voinea defeated fifth-seeded Stefan Koubek in the final of the 1999 Brighton International in Bournemouth to win his only singles title at an ATP Tour event.
Between 1995 and 2003 Voinea played in 12 Davis Cup ties for the Romania Davis Cup team and compiled a record of 10 wins and eight losses, all of which were singles matches.