Background <p>Seasonal variations significantly influence household food insecurity, especially in developing countries like Ethiopia, yet this issue remains underexplored in the Ethiopian context.</p> Objective <p>This study aimed to assess seasonal variation in the prevalence of household food insecurity and its associated factors in the West Gojjam Zone, Ethiopia.</p> Methods <p>A longitudinal study was conducted from December 2023 to September 2024, using multistage stratified sampling to select 844 women from three districts. Data were collected during the seasonal transitions (September, June, March, and December) via interviewer-administered surveys. Data were analyzed using EPI Data 4.3 and SPSS v. 29, with multivariate logistic regression to identify food insecurity factors.</p> Results <p>Food insecurity prevalence varied seasonally: 79.3% in June, 49.8% in December, 59.1% in September, and 69.9% in March. Key factors associated with food insecurity included the season (June: AOR = 2.27, March: AOR = 1.34), Orthodox religion (AOR = 21.5), low economic status (poorest: AOR = 5.80, poorer: AOR = 5.65, medium wealth: AOR = 4.3), non-use of agricultural inputs (AOR = 1.53), poor knowledge of food insecurity (AOR = 0.38), and low dietary diversity (AOR = 2.73).</p> Conclusions <p>Significant seasonal variations in food insecurity were observed, with factors such as season, Orthodox religion, economic status, agricultural input use, food insecurity knowledge, and dietary diversity playing crucial roles. To reduce food insecurity, seasonal food security programs, improved access to agricultural inputs, income diversification, and enhanced nutrition education are essential.</p>