First mentioned in a will dated at 959, Aveiro was granted the right to hold an annual "feira franca " (a duty-free market) in 1434, which is still held today under the name of "Feira de Março" (March Fair). Some years later, in 1472, Princess Joana, daughter of King Afonso V, entered the Convent of Jesus where she died in 1490. The Princess's stay in Aveiro was vital to its development.

People engaged in salt extraction, fishing and sea trade were attracted by Aveiro's excellent location. In 1504, boats built in its shipyards were already sailing to Newfoundland and Aveiro acquired new prosperity through codfish industry. The formation of the lagoon, which is today one of the main attractions of Aveiro, dates back to the 16th century. Unfortunately, by the end of the same century, strong storms silted up the harbour mouth, dealing a deathblow to Aveiro's sea trade and leading to a huge migratory movement and severe economic and social crisis.

Enjoying the status of city and seat of diocese since the 18th century, Aveiro prospered rapidly after the establishment of its university in 1973.