Background: There has been a limited decline in undernutrition rates in Bangladesh. Household food security is one of the major factors. Despite Bangladeshs remarkable progress in agricultural production, household food insecurity persists, especially in rural areas. This study examined household food insecurity and household dietary diversity in the rural areas of northwest Bangladesh during the COVID-19 Pandemic. Methods: The study used data from baseline assessment of a large cluster randomized trial on social protection and child undernutrition. The data were collected from December 2020 to October 2021 from 2756 households. The Household Food Insecurity experience scale (FAO 2018) was used to assess household food insecurity, while the household dietary diversity was measured by the household dietary diversity score (FAO 2006). Results: Nearly 35% of all households were moderately or severely food insecure. The prevalence of food insecurity among land-rich farmers or professionals was much lower (26%) than among families of other occupations (42%). The prevalence of food insecurity among families with educated women was almost half (22%) compared to families with uneducated women (45%). The mean HDDS was six food groups indicating that families had, on average, access to 6 out of twelve food groups daily. The dominant consumed food groups were cereals (90%), fish (75%), and vegetables (79%), while the lesser consumed food groups were eggs (28%), legumes (22%), meat (25%), milk (38%). We did not find any significant seasonal variation in household food security and dietary diversity. Discussion: Our findings showed that the percentage of households experiencing moderate to severe food insecurity during the pandemic was more significant than the pre-pandemic national average (15%). Most families relied on less expensive food choices during the pandemic period. The seasonal poverty period (Monga in the local language) did not further affect food security and dietary diversity.