This study investigated the influences of critical thinking disposition (CTD) on EFL undergraduates’ situated academic writing self-efficacy (SAWSE). A total of 243 Saudi students completed Yoon’s Critical Thinking Disposition (YCTD) instrument and the Situated Academic Writing Self-Efficacy Scale (SAWSES). The findings revealed that students had medium levels of CTD (M=3.26, SD=0.56) and SAWSE (M=3.20, SD=0.68). Eagerness, fairness, and objectivity scored the highest levels on CTD, whereas prudence had the lowest level. In addition, findings revealed significant differences in levels of situated academic writing self-efficacy among students who had high, medium, and low levels of critical thinking disposition. The correlations between subscales of CTD and SAWSE were all positive and statistically significant. Besides, the self-confidence subscale of CTD had the most significant impact on all three aspects of SAWSE. The study paved the way to understand how students’ situated academic writing self-efficacy changes as a result of critical thinking deposition. Implications for EFL teachers and future directions were discussed.