The settlement of Łęczyca had grown up by the 9th century. During the period of 1138-1148 it was a seat of princess Salomea, Bolesław’s III Wrymouth widow. Before 1267 Łęczyca was granted town privileges in accordance with the German town law. The town became the capital of the Principality of Łęczyca. Both the nobility and the clergy held numerous congresses there. In 1331 the Teutonic Knights burnt the town down and in 1352 it was joined to the Crown of the Kingdom of Poland. In 1420 the Czechs offered their crown to Jogaila, King of Poland in Łęczyca. In the mid-17th century Swedish troops destroyed Łęczyca.
Since 1793 Łęczyca was part of the Prussian partition, since 1807 it was included in the Duchy of Warsaw and since 1815 it belonged to Congress Poland.
During World War I, in 1914, fierce fights took place in Łęczyca. The town was then taken over by German troops.
During World War II, in September 1939, in the vicinity of Łęczyca violent struggles between the Polish forces and the German army took place in the Battle of the Bzura, the biggest battle of the 1939 September Campaign.