Collserola Park in northeastern Spain is an 8,000 ha Mediterranean forest park surrounded by the Barcelona metropolitan area with a population of some three million inhabitants. Wild boar Sus scrofa are common in Collserola and cause specific management problems. We obtained information on their activity and habitat use in different areas of the park by use of two field methods: prospecting of non-linear transects at night on foot and periodic monitoring of sign-survey plots. Prospecting of routes on foot provided information on summer nocturnal activity in different natural and semi-natural environments: feeding activity takes place mainly during 00:00–05:00, and the maximum amount of movements was registered during 20:00–00:00 and at dawn. Wild boar feeding activity was significantly lower on dry slopes than in other habitat types such as riparian woodland, valley bottoms and agricultural areas. Pellet-group density varied significantly between habitats, being higher in agricultural habitats, intermediate in riparian woodland and lowest on wooded slopes. In general, pellet-group density was higher on level ground than on slopes. The mean surface area rooted by wild boar was less than 5% in all survey periods. Rooting activity, which was dominated by surface rooting, was highest in winter and lowest in summer when soil conditions for rooting were poorest. Rooting activity varied significantly between habitat types, and distinct seasonal patterns were observed within individual habitat areas. The results we obtained support the view that the summer is a critical period for wild boar in Mediterranean environments and highlight the importance of ensuring certain scarce habitats for foraging activities during this season.