The history of ancient Niasvizh is rather complicated. It was considered for a long time that Niasvizh was first mentioned in the chronicles in 1223, when Yuri Niasvizhski was mentioned among the Russian princes that had died in a battle with the Mongols on the Kalka. However, most specialists consider that the chronicler meant either Niesviezh in Vladimir-Suzdal lands or Niesvich in Volyn. It is more correct to consider that the history of the modern Belarusian town began in 1445, when «the settlement of Niasvizh» was first mentioned in the documents (Grand Duke Casimir passed it to Nickolai Nemirovich). Later Niasvizh was the property of the Soltan, Montygirdovich, and Kishka families. In 1513 Anna Kishka married Yan Radziwiłł. Niasvizh was the dowry that she brought to her husband. In 1533 the town became the property of this magnate family.
In the middle of the 16th century there was a Calvinist church and protestant printing house in Niasvizh. The first books in Belarusian on the territory of modern Belarus were printed there: Catechism, and On the justification of sinful men in front of God. At the end of the 16th century Mikołaj Krzysztof Radziwiłł Sierotka (the Orphan) rebuilt the town according to Western Europe architecture rules: rectangular layout with entry gates on the axes of the main streets; market square with a Town Hall; around the town — a soil bund and a moat. In 1586 the town received Magdeburg rights and its own coat of arms. It was a shield divided into two parts. On the right part — a half of a black eagle on a golden background; on the left one — ten oblique stripes, light blue, red and golden. Slightly changed the coat of arms was used in different historical periods and survived till now. Mikołaj Krzysztof Radziwiłł also made Niasvizh a big centre for spread of Catholicism. A Jesuit collegium, Benedictine and Bernardine monasteries were founded here. Yan Maria Bernardoni, an architect, author of a number of famous buildings worked in Niasvizh at that period, as well as Tomash Makouski, an artist and engraver, who worked here on the preparation of the map of the Great Duchy of Lithuania for publishing.
In 1628-1629 the first Niasvizh inventory was prepared, which survived till now. According to it there were 177 Christian and 27 Jewish houses in the town. In 1673 there were 366 houses and about 2.4 thousand dwellers. By the end of the century a Dominican church had appeared in Niasvizh, and Jesuit and Benedictine monasteries were built not far from the town. In the 17th-18th centuries Niasvizh was an important trade and handicraft centre. There were tailor, merchant, furrier, bricklayer and potter, weaver, shoemaker shops, as well as a locksmith-blacksmith-coppersmith shop here. Fairs were organized here annually and lasted 2 — 4 weeks.
The development of the town was often interrupted by wars. In 1655 and 1660 it was robbed by Moscow tsar army. In 1706, in March, there was a battle in the town streets between Swedish dragoons and Zaporozhian Cossacks in which the Cossacks were defeated. The town was burnt up. After the seizure of the castle in May that year the Swedish army destroyed the survived buildings. According to the documents the entire town except Catholic churches and monasteries was turned into ashes.
In 1724 Michał Kazimierz Radziwiłł Rybeńko, having finished his educational journey of Europe, solemnly entered Niasvizh. It symbolized the beginning of the town revival. In the middle of the 18th century several manufactories were opened in the town, as well as a cadet corps and a publishing house; the castle and Town Hall were rebuilt. A shooting contest was annually held among the town dwellers. The winner received the title of the king of the hammer and was exempted from taxes. At that time Niasvizh was visited by architects, artists, musicians who could achieve a high position in society. Thus, a courtier artist Casimir Lutnitski not only owned three plots of land but was elected burgomaster. It was here in Niasvizh that a watchmaker Yevno Yakobson designed a mechanical calculation machine.
In 1793 after the second partition of the Polish-Lithuanian Commonwealth Niasvizh became part of the Russian empire. At first it was a district centre, and since 1796 — a non-administrative town of Minsk governorate. The 19th century is known for gradual dissolution of Catholic monasteries, and turning Catholic churches into Orthodox ones. In 1875 a teachers’ seminary was opened in Niasvizh, where primary school teachers were trained. There was also a meteorological station, museum, and a library there. Among the famous graduates of this institution are an ethnographer Adam Bahdanovich, poet Yakub Kolas, writer Kuzma Chorny, and others.
In 1921 according to the Peace of Riga Niasvizh became a part of the Polish state. The town kept its multinational character. There were Polish public and culture organisations, Jewish religion schools and education unions. At the beginning of the 1920s there was a Belarusian gymnasia here.
On 17 September 1939 the Red Army entered the town. In January 1940 Niasvizh became a district centre of the BSSR. In June 1941 it was occupied by the German army. During the occupation more than 6 000 people died (mostly Jews). On 2–4 July 1944 after hard severe battles the town was liberated by the 65th Army troops and partisans.