In the early middle ages Lesko was located in a densely populated area. It was first mentioned in a source of 1436. Around 1470 it was given civic rights. It was the first town in the Bieszczady, located on Magdeburg Law. Other towns in this area came into being much later.

Lesko was an economic and administrative centre of great Kmita estates and later of Stadnicki, Ossoliński and Krasicki families. The biggest growth of Lesko took place in the first half of the 17th century. Being the residence of noble families it played an important role in cultural life of the region. It was also a religious centre of Roman-Catholic Church, Greek-Catholic Church and Jewish faith. After the first partition of Poland in 1772, Austrian authorities placed the seat of Dystrykt in Lesko (administrative region), and then cyrkul (district) including almost whole area of Ziemia Sanocka. In 1867 poviat starosty was created, and as a result Lesko became a seat of one of the biggest, until World War II, poviats in Poland. During the war Lesko also played an important role of administrative district. From 1939 to 1941 Soviets created a region here, and Germans (1941 – 1944) the seat of so-called komisariat wiejski (country Commissioner).

After liberation as a poviat town it played an important role in building and economic management of the area. Lesko had – first in the Bieszczady – grammar school, woodwork technical school, a technical school of forestry and a technical school of farming. As an administrative centre, Lesko contributed to reconstruction of many roads (two Bieszczady ring-roads, called Mała i Duża Pętla Bieszczadzka), water power stations in Solina and Myczkowce and also holiday and sanatorium resort in Polańczyk.

In 1998 the first phase of gas supply in the Bieszczady was finished. Gas distribution station was built in Lesko, gas was lead to the town and the borough of Lesko, and partly to Baligród borough. Decision of Government of the Republic of Poland of 7th August 1998 formed one poviat in the Bieszczady with the seat in Ustrzyki Dolne. It caused opposition of five out of eight boroughs of the poviat: Baligród, Cisna, Lesko, Olszanica, Solina. Common actions before elections caused that most of newly chosen council of poviat were the followers of the idea of creating poviat in Lesko.

So on the 12th of May 1999 the council of the Bieszczady poviat applied to Rada Ministrów (the Cabinet) for division of the Bieszczady poviat into two separate ones with seats in Lesko and Ustrzyki Dolne. After three years of of hard work of poviat council, citizens’ committee for protection of poviat, Lesko citizens and of neighbouring boroughs, on the 1st of January 2002, Lesko poviat came to life (separated out of Bieszczady poviat).