Vilassar de Mar is a municipality located in the Maresme region, with an area of 4 km². It is bordered to the north by the municipality of Cabrera de Mar and Vilassar de Dalt, to the east by the municipality of Cabrera de Mar, and to the west by Vilassar de Dalt and Premià de Mar.

The climate is Mediterranean, characterized by warm summers and mild winters. Precipitation is concentrated in spring and autumn. The plant population is of Mediterranean type.

The inhabitants of Vilassar de Mar are popularly known as penjaases, a name that comes from a legend that explains that some herbs grew in the bell tower of the church and its inhabitants did not know how to remove them. The villagers thought that a donkey could eat them, they made him climb up with a rope tied around his neck and the animal ran away. This is where the word "penjaases" comes from.