The reign of Theodore Svetoslav is connected with the internal stabilization and pacification of the country, the end of Mongol control of Tarnovo, and the recovery of portions of Thrace lost to the Byzantine Empire since the wars against Ivaylo of Bulgaria.

Theodore Svetoslav pursued a ruthless course of action, punishing all who stood in his way, including his former benefactor, Patriarch Joachim III, who was accused of treason and executed. In the face of the new emperor's brutality, some noble factions sought to replace him with other claimants to the throne, backed by Andronikos II. A new claimant appeared in the person of the sebastokratōr Radoslav Voïsil from Sredna Gora, a brother of the former emperor Smilets, who was defeated, and captured by Theodore Svetoslav's uncle, the despotēs Aldimir (Eltimir), at Krăn in about 1301.

Another pretender was the former emperor Michael Asen II, who unsuccessfully tried to advance into Bulgaria with a Byzantine army in about 1302. Theodore Svetoslav exchanged thirteen high-ranking Byzantine officers captured on Radoslav's defeat for his father George Terter I, whom he settled in a life of luxury in an unidentified city.