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 Valparaíso 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.The marine otter (Lontra felina) inhabits almost the entire coastal border of Chile. Its population density and how it responds to the several current anthropic threats are almost unknown. The objective of this study was to analyze and compare the patterns of habitat use, sightings and behavior of the marine otter in two coastal areas of the Valparaíso Region, Cachagua and Quintay. A total of 20 simultaneous visits to these localities were performed, 10 in summer and 10 in autumn. The observation area of each locality was divided into virtual quadrants parallel to the coast to evaluate the habitat use of the marine otter. We evaluated the number of sightings, the type of behavior and its duration. The number of sightings was significantly higher in Quintay. There was significantly more movement in Quintay than in Cachagua during the summer. On the other hand, the time occupied by the animals in the three behaviors was similar between seasons in Quintay. Instead, the movement and diving were less frequent in Cachagua during summer. The results suggest that the marine otter can adapt to changes in the conditions in its surroundings.