Archeological finds from Sieraków and its region date back to 8000/5000 years BC.
In the Middle Ages the town was rapidly developing due to its location, which was good for crossing the Warta river. The first note about Sieraków dates back to 1251. The town was granted a town charter before 1388.
The 17th century saw a peak development of Sieraków, mainly thanks to the Opaliński family. There were many fine buildings erected, among other constructions an exceptionally treasured church of the Friars Minor of the Observance. The Opaliński Manor House was one of the most magnificent in Poland. The last but one heiress of the town from the Opaliński family was Katarzyna, the wife of King Stanisław Leszczyński. Their daughter, Maria, became the wife of the King of France, Louis the 15th.
In 1829 the first stable of fine stallions was founded in Sieraków.
In the 1930s the town started to gain reputation as a popular holiday resort.