Slow-onset disasters, a neglected climatic event, affect the agricultural sector in Southeast Asia and threaten regional food security. Improving food security in slow-onset disasters requires policy development by both regional and national governments. Despite this articulated need, very little research on the national and regional food security policies in slow-onset disaster events has been undertaken. Focusing on Southeast Asia, this paper aims to (i) review existing policies to support food security in slow-onset disasters; (ii) identify strengths, weaknesses, and gaps in the existing policies; (iii) explain the policy window on food security in slow-onset disasters. An analytical framework of eight components of food security was adopted for the content analysis of 39 related policy documents collected from 11 countries in Southeast Asia and the Association of Southeast Asian Nations. The study found that none of the 39 policies directly targeted improving food security in slow-onset disasters. Existing policies to support food security in slow-onset disasters were incorporated in the context of climate change or national target programs on green development, agricultural development, nutrition, and famine. Our analysis also revealed that existing policies primarily focus on the first two pillars of the food security framework: food availability and access, with a predominant emphasis on availability. However, the third pillar, food utilization, is often overlooked. This study recommends developing a comprehensive policy to address protracted food insecurity, particularly among vulnerable populations in areas impacted by slow-onset disasters.