Scent marking behavior in mammals is related with both inter and intra-specific communication. Several otter species are known to communicate via scent marking, but a couple scent marking has not been documented in the Neotropical Otter (Lontra longicaudis). We obtained field observations of scent marking behavior in Neotropical Otters over two years using camera traps along waterways in the eastern Brazilian Amazon. Our results reveal the use of sandy substrates on islands and river margins for intra-specific communication between otters. Most records (62.5%) were from solitary adults. We document multiple independent records of adult otters digging to scent mark with urine and couple behavior of males urinating on top of female’s fresh urine in newly dug shallow craters. We also demonstrate behavioral plasticity of this species evidenced by camera traps recording terrestrial activity during both day and night. Our results contribute to improve the knowledge of the behavior of this otter species in the wild and can potentially be applied to improve ex-situ welfare of captive otters.