Mancini was born in London, and was originally named
Terry Seely. His father (who was
Irish) died when Terry was seven and his mother remarried, changing his surname to that of his stepfather. He began his career with
Watford, joining the club in 1960 before being released midway through the
1965–66 season. After a 20-month spell in South Africa playing for
Port Elizabeth City, he returned to London in November 1967 to join
Leyton Orient. He spent four seasons with Orient, winning a
Third Division medal in
1969–70. In October 1971 he signed for
Queens Park Rangers, and helped them to promotion to the
First Division in
1972–73. Born and brought up in England, after a chance conversation with QPR teammate
Don Givens, Mancini found out that through his Irish father, he could play for the
Republic of Ireland. He won his first cap against
Poland in 1973 and went on to win five in total. Mancini later reported that when he first appeared for the Republic of Ireland, he did not realize that the band was playing the
Republic's national anthem, having never heard the tune before. Memorably for him, Mancini's one international goal came at the Maracana in a friendly against Brazil ahead of the 1974 FIFA World Cup. He was sent off on his last appearance, a 3–0 win in
Dalymount Park over the
Soviet Union on 30 October 1974: Mancini received a straight red card for punching
Volodymyr Kaplichny ("[I] took half his nose off") in retaliation for persistent kidney punches. Mancini signed for
Arsenal in October 1974 for £20,000. Having made his debut against
West Ham United on 26 October 1974, he played for Arsenal for two seasons, recording 62 appearances. However, after Arsenal's worst performance in over forty years in the league (17th) in
1975–76, Arsenal manager
Bertie Mee resigned. Mancini was deemed surplus to requirements (being nearly 34) by Mee's replacement
Terry Neill, and he was released on a
free transfer in September 1976. He joined
Aldershot and played a single season with them. He ended his career in the
NASL, playing one summer with the
Los Angeles Aztecs before returning to England ==Non-playing career==