The Tvarditsa municipality is situated on an area of 442.5 sq. km in the westernmost part of the District of Sliven. It encompasses the southern slopes of the Elena-Tvarditsa Part of the Balkan, the hills of Mezhdenik (in the Sredna Gora Mountain), a part of the valley of the Tounja River and a part of the Zhrebchevo Dam. The municipality's central part is occupied by the Tvarditsa and Shivachevo Hollow Field. It borders the following municipalities: Sliven to the east, Nova Zagora to the south, Gourkovo (the District of Stara Zagora) to the west and Elena (the District of Veliko Tarnovo) to the north. The geographical location of the Tvarditsa municipality together with the sub-Balkan transport corridor - a railway and a highway Sofia - Karlovo - Bourgas, which passes through the municipality, favours the development of the transport and economic connections not only with the neighbouring municipalities, but also with the districts all over Bulgaria.
