ABSTRACT The marine otter (Lontra felina) inhabits almost the entire coast of Chile. Its population density and its response to several anthropic threats are almost unknown. The objective of this study was to analyze and compare the patterns of habitat use, the frequency of sightings, and behavior of the marine otter in two coastal areas of the Valparaiso Region: Cachagua and Quintay. Twenty simultaneous visits to these localities were made, 10 in summer and 10 in fall. The observation area of each locality was divided into quadrants parallel to the coast to evaluate the marine otter habitat use. We evaluated the number of sightings, the type of behavior (displacement, diving, or feeding) and the duration. The number of sightings was significantly higher in Quintay. There was significantly more displacement in Quintay than in Cachagua during the summer. However, the time spent by the otters in the three behaviors was similar between seasons in Quintay. Moreover, the displacement and diving were less frequent in Cachagua during summer. The results suggest that the marine otter can adapt to changes in the conditions of its surroundings caused by humans.