Food insecurity is a global public health issue associated with noncommunicable diseases. Individual factors are strongly associated with food insecurity, but there is limited literature on the broader impact of both the social and food environments on food insecurity in non-English speaking European countries, given that the research was predominantly conducted in Anglophone settings. In addition, these studies have mostly been conducted in urban areas. Therefore, this study aimed to identify the main determinants of food insecurity among adults living in peri-urban areas in Flanders, Belgium. Data on socio-demographics, neighborhood social cohesion, social isolation, and perceived food environments were collected from 567 adults through a self-administered questionnaire, and objective data on the food environment were obtained through (commercial) databases on food outlets. Food insecurity was measured using the USDA Household Food Security Survey Module. Multivariable logistic regression models revealed that lower socioeconomic status (OR14.11,95%CI:4.72;61.11), reasonable (OR4.16,95%CI: 2.11;8.47) to poor and very poor (OR6.54,95%CI: 2.11;8.47) subjective health status, and living in private (OR7.01, 95% CI:3.0;17.0) or government-assisted (OR6.32,95%CI: 3.13;13.26) rental housing significantly increased the odds of food insecurity. Additionally, residing in a neighborhood with low (OR2.64, 95% CI:1.13;6.26) to medium (OR2.45,95% CI:1.21;5.11) social cohesion, having a neutral opinion (OR4.12,95%CI:1.51;11.54) about the availability of fruit and vegetables in one's neighborhood, and having an opinion that fruit and vegetable prices are too expensive (OR5.43,95% CI 2.26;14.4) significantly increased the odds of experiencing food insecurity. This study underscores the need for policies that consider factors related to social and food environments, in addition to individual factors, to effectively address food insecurity.