Herbivore foraging is influenced by spatial and seasonal changes in the production of leaves and fruits. To understand how herbivores respond to these changes, it is necessary to identify their habitat preferences and how they use the vegetation available. In the Neotropical region, one of the largest terrestrial herbivores is the lowland tapir (Tapirus terrestris), a species important for its dual role as browser and seed disperser. The objective of this study was to determine the species and plant components (leaves, fruits) utilized by T. terrestris in different time periods and habitats, in relation to changes in food availability in the north-western Amazon. Tapir diet was established through identification of browsing signs and faecal analysis, from data collected in the field during the months of March, April, August and September of 2015. Plant species availability for browsing was sampled in ten 2 × 50-m transects and fruit productivity was estimated in linear transects (~9 km). We found that T. terrestris mostly consumed vegetative parts, i.e. fibre (70–90%), and to a lesser extent fruits (10–30%). Food consumption was selective and concentrated in habitats with higher availability of preferred plants. When fruit intake increased, selectivity in browsing became more intense and limited to preferred species. This information, coupled with our findings about seasonal differences in browsing vs. frugivory patterns, provides valuable knowledge for understanding how environmental heterogeneity may influence the foraging ecology of the lowland tapir.