He served as secretary to the hospodar of Moldavia Scarlat Callimachi, and in early 1821 he was appointed Ottoman envoy to Paris.
On his way, however, he received news on the outbreak of the Greek War of Independence, and went secretly to Greece.
Negris arrived on the island of Spetses in Ottoman dress, and was almost lynched by the crowd, but was saved by Neofytos Vamvas.
Theodoros joined fellow Phanariotes Alexandros Mavrokordatos and Kostakis Karatzas.
As the power of the Areopagus declined in favour of the central provisional government, so Negris too began to be sidelined and lose his influence.