The Bolyarovo municipality is situated in one of the country's regions with themost unpolluted environment. It is located in the south part of the Yambol district upon the north slopes of the Stranja Mountain. It encompasses a part of the Tounja Hilly Area, the Dervent elevations and the south slopes of Bakajitsite. It encompasses an area of 667 sq. km and constitutes 0.06% of the Republic of Bulgaria's territory. It borders the Republic of Turkey to south (55 km of common boundary), the Elhovo municipality to the west, the municipalities of Tounja, Yambol and Stranja to the north and the Bourgas district (the Sredets municipality) to the east.

There already was human presence on the present territory of the Bolyarovo municipality in early antiquity. Traces of Thracian settlements have been discovered on the land of the villages Krainovo, Iglika, Popovo, Dennitsa and Kamen Vrah. There are traces of ancient copper-ore works in the Trofalashkite Doupki area. An important road artery used to lead from Sliven and Yambol through the village of Popovo, west of Bolyarovo, Lalkovo and Golyam Dervent, to Odrin.

Archaeological excavations by the village of Voden

 The ottoman stronghold Pashakyoiskoto Kale, which was probably built earlier by the Bulgarian Khan Omourtag, and the late-antiquity fortress  Potamoukastel by the village of Voden outline another important road. There are traces of a medieval settlement in the Eki Joumaya area one kilometre northwestwards of the village of Dennitsa. Fragments of structural clay products and pottery, which are typical of both the Second Bulgarian kingdom and the first centuries of the Ottoman rule, can be found on the surface of the terrain. The renowned Trite Kaleta (the Three Strongholds) by the village of Voden had an important strategic role in medieval Bulgaria.

The village of Bolyarovo was founded in the national revival period as the landed estate of an Ottoman pasha (administrator and military leader). During the same period the village of Voden (then Derekyoy) took an active part in the church struggles of the Bulgarian people. It was the first to join the Bulgarian Exarchate, while the neighbouring Sharkovo (then Golyam Boyalak), Malko Sharkovo (then Malak Boyalak) and Gorska Polyana (then Ailajik) remained under the Greek Patriarchate. 

Although it was away from the country's large substantial centres, the Bolyarovo region did take part in the manifestations of the Bulgarian movement for national liberation. The local population has preserved to our day the memories of the Pehlivanov brothers from the village of Bolyarovo (then Pashakyoy) - rebels, killed by the Turks, of the detachment of Stoyan Stefanov from Voden (then Derekyoy), of the great patriot and rebel Old Nikola Ouzunov from the village of Stefan Karajovo (then Ichme), of the organizer of the West-Stranja Revolutionary Committee and struggler for church and national independence Kourti Drazhev, who was exiled to the Diarbekir fortress by the Turks. The village of Popovo (then Papaskyoy) is the birthplace of the national hero Inje Voivoda. An object of local and national pride is Stefan Karaja, who was born in the village of Stefan Karajovo (then Ichme). 

The village was renamed from Pashakyoy to Bolyarovo in 1934. It acquired the statute of a town-type village in 1963 and was proclaimed a town in 1974. It was on the territory first of the Yambol district, then of  the Bourgas district, and since the latest administrative division of the country in 1999 has been in the Yambol district.

 Soils

In the hilly part of the municipality prevail the maroon soils and the brown forest soils, and in the valley of the Popovska River - Mediterranean black soils and leached Mediterranean black soils.

Mineral Resources

The  industrial stock of ores and minerals on the municipality's territory is scanty. There are stocks of copper ores on the land belonging to the villages of Golyamo Kroushevo and Iglika and of limestone on the land belonging to the villages of Voden and Krainovo. The mineral springs with a flow rate 13 l/sec by the village of Stefan Karajovo have been surveyed and piped. By its chemical constitution the water is hydrocarbonate, potassium-magnesium with mineralization 1.5 l/sec, with proven healing properties similar to those of the water in Karlovi Vari in the Check Republic and Kislovodsk in Russia. Its properties and its flow rate, and also the existing balneotherapy centre with 240 beds allow the development of a health resort.