<p>Agriculture takes the lion’s share to Ethiopia’s economy, serving as the main source of employment, income, and food security for smallholder farmers. However, the sector remains highly vulnerable to climate change due to its heavy reliance on erratic rainfall. This study aimed to identify the determinants of Climate-Smart Agriculture (CSA) practice adoption and assess its impact on the food security of smallholder farmers. A cross-sectional survey of 260 smallholder farmers was conducted using multistage sampling. The Multivariate Probit Model was employed to identify adoption determinants, while the Endogenous Treatment Effect model was used to estimate CSA’s impact on food security. Findings revealed that farmers were most likely to adopt crop diversification (50.4%), followed by water management (49.9%) and soil and land management (48.3%). The joint adoption probability was 3.02%, while the likelihood of adopting no CSA practices was only 4.5%, indicating strong complementarities among practices. The analysis confirmed both synergies and trade-offs in CSA adoption patterns. The Endogenous Treatment Effect model demonstrated that CSA adoption significantly improved food security, increasing daily calorie intake by 217.59&#xa0;kcal per capita among adopters compared to non-adopters. The results were robust, supported by strong instrument relevance and model validity. The study concludes that enhancing CSA adoption can significantly improve food security and smallholder livelihoods. Therefore, promoting CSA through field demonstration by development agent works, strengthening cooperatives, irrigation investment, farmer training, and access to affordable credit is recommended to empower farmers, enhance productivity, and support sustainable agricultural development in line with national and global climate resilience goals.</p>