Teodossiy Simeonov was born on August 12, 1946 in Pleven.
He graduated from the Faculty of Law at the Kliment Ohridski University of  Sofia.
Between 1978 and 1984 he worked as a legal adviser at the motor transport enterprise in Pleven.
In the years following 1984, until 1990, he was a criminal process lawyer in the town of Nikopol.
1990 - 1996 - he was Lawyer and Chair of the Bar in Pleven. Specialist in grave criminal cases.
He claims to have entered politics on account of his two grandfathers who both had been members of parliament. His father had been detained in the forced-labour camps of Kotsian and Belene.
Teodossiy Simeonov was elected MP of the Union of Democratic Forces in the 38th National Assembly, 15th Pleven Constituency ticket. Member of the Parliamentary Committee for Legal Matters and Anti-corruption Legislation, the Committee for Agriculture, Forests, and Agrarian Reform, and the Committee for Crime and Corruption  Prevention.
In October 1997 he headed the Interim Committee for stripping the immunity of BSP deputy Krastyo Trendafilov.
Married, with two children. His wife is a garden and low-rise construction designer.
Working knowledge of German.
He has engaged in motor cycling and has participated in races

On 18 December 1999 he was re-elected chairman of the local leadership in the Pleven organization of the UDF.
T. Simeonov was appointed Minister of Justice upon the December 1999 cabinet reshuffle.