Food and nutrition security is the regular and permanent access to quality food in sufficient quantity. The aim of this study was to estimate the prevalence and factors associated with food insecurity in households with children under five in the Amazon frontier Brazil - Peru. The study was conducted in 352 households in Assis Brasil (Brazil) and 89 households Iñapari (Peru), finding a prevalence of food insecurity of 40.6 % and 38.2 %, respectively ( p = 0.856 ) . In Assis Brasil, having domicile with wood fl oors or land increased by 2.47 times the odds of food insecurity compared to cement fl oors, ceramic or quarry tiles . Belonging to the poorest tertile increased the chance of food insecurity in 6.04 times ( p < 0.001 ), and the increment of each new resident increased by 37 % the chance of food insecurity in the household . In Iñapari, only living in house made of wood or with a wood fl oor was associated with food insecurity, showing that income is still the main factor associated with food insecurity in the Amazonian borders.