According to archaeological research, the territory of Saldus was inhabited by ancient Couronian tribes in the second millennium BC. The centre of the defended settlement was the castle, which stood on the hillfort next to Lake Saldus until the 13th century.
For the first time Saldus was mentioned in the Cours Treaty in 1253 whereupon the area (“Terra inter Schrunden et Semigallian” – the land between Skrunda and Zemgale) was given to the Livonian Order.
Saldus bore the German name Frauenburg for almost four centuries. A stone castle for the Order of German Knights was built in the 15th century, and a new settlement appeared near the castle.
In the 16th-17th centuries the area of Saldus became part of Duchy of Courland and Semigallia. In 1638 Saldus was the first estate of Duke Jacob (gouverned 1642-1682) during whose governance an iron furnace, a cannon foundry, a linen weaving mill, a leather processing factory, a sawmill, and a potassium production unit were operating in the area of Saldus. The Ciecere and the Venta rivers were used to deliver the produced goods to Skrunda and Ventspils. A post station on the road Jelgava-Klaipēda was founded in Saldus in 1632 and it promoted the development of the settlement.
During the Northern War the Frauenburg castle and the settlement were completely destroyed. In 1795 Saldus along with the rest of Kurzeme became part of the Russian Empire.
In the second part of the 19th century Saldus began to develop as a market place. First 42 building plots were measured from the land of Saldus estate and were sold in 1856.
In 1917 Saldus received full rights as a town. In 1919, Saldus was the first town in Latvia to be freed from Bolsheviks by the battalion of Latvian National Army led by Oskars Kalpaks. On 25 November 1919, the town was freed from the Bermont army. The town expanded after the Freedom Fights, and the town’s economy started to develop. At the final stage of World War II the town was in the middle of continuous fights in the Courland Pocket. On 8 May 1945, the USSR forces entered the town, and the Soviet occupation started. In 1991 Latvia regained independence, and economical and political changes in Saldus followed.
In July 2009 Saldus municipality was formed by the amalgamation of 16 local governments – Ezere, Jaunauce, Jaunlutriņi, Kursīši, Nīgrande, Novadnieki, Lutriņi, Pampāļi, Ruba, Saldus, Šķēde, Vadakste, Zaņa, Zirņi and Zvārde parishes, and Saldus town.

In 2021, Brocēni municipality was added to Saldus municipality. After the amalgamation, the current Saldus municipality consists of two towns – Saldus and Brocēni, and 19 parishes – Blīdene, Ciecere, Ezere, Gaiķi, Jaunauce, Jaunlutriņi, Kursīši, Lutriņi, Nīgrande, Novadnieki, Pampāļi, Remte, Ruba, Saldus, Šķēde, Vadakste, Zaņa, Zirņi, Zvārde.