The coronavirus pandemic protracted disruption of in-person schooling, sports and other activities leading to obesity that could have long-lasting impact on children’s health. As a result, education has changed dramatically, with the distinctive rise of E-learning. Children are snacking more, exercising less. Their increased screen time, sedentary life style and inadequate sleep anticipated weight gain during Lockdown that could lead to complications. To study the impact of the COVID-19 lockdown on increased weight gain in children. A cross-sectional study was conducted from March to May 2021 at tertiary care hospital, Thandalam among 2000 children between the age of 3–15 years on weight gain during COVID-19 Lockdown. A questionnaire requesting demographic and Anthropometric details was circulated. BMI percentiles were calculated, totalled and compared between pre-school closing and school closing period. Paired t-test was done. p value < 0.05 was considered statistically significant. Out of 2000 children, 308 were excluded. Male preponderance was noted. Age range was between 3 and 15 years with mean age being 8.5 years. Study revealed significant differences in variables such as body weight, body mass index before and after lockdown. Post-lockdown, the mean body mass index (BMI) increased among all participants from 17.32 to 17.80 kg/m2 (p < 0.001). Obesity definitely has a proportional impact on the children’s Quality of Life (QOL). It is important to address childhood obesity, which if neglected may lead to long-term profound complications of higher eminence than the actual COVID-19 infection. The prevention and management of childhood obesity should be set as a priority at an individual, community and population level during this pandemic.