Lockdown caused by the COVID-19 pandemic may have influenced feeding behaviour and lifestyle in children and adolescents. The purpose of this study was to analyse feeding behaviour and lifestyle in children and adolescents one year after lockdown by the COVID-19 pandemic in Chile. In this cross-sectional study an online survey was implemented in 1083 parents and caregivers regarding their children’s feeding behaviour and lifestyle and sociodemographic background. The results showed that “eat breakfast daily” (89.2%), “not overnight food intake” (69.9%) and “not fast-food intake” (66.0%) were the most frequent reported feeding behaviours, particularly in pre-school children. Respondents declaring healthy feeding behaviours and lifestyle were 23.4 and 23.7%, respectively, with no significant differences by sex. In pre-school children, families with three or fewer members and parents or caregivers with an undergraduate or postgraduate degree reported a significantly better feeding behaviour and lifestyle compared to families with more than three members and parents or caregivers without an undergraduate or postgraduate degree. In conclusion, the pandemic lockdown had a negative impact in lifestyle in children and particularly in adolescents. Healthier feeding behaviour was associated with fewer family members and parents or caregivers with at least an undergraduate degree.