Background: Occupational exposure to aluminum can potentially cause health problems for workers in the aluminum foundry industry, which might associate with cognitive impairment. However, studies in the informal aluminum foundry industry are still very limited. This study aimed to determine the relationship between aluminum exposure and cognitive impairment in informal aluminum foundry workers. Methods: This study used a cross sectional design with logistic regression analysis. Seventy-nine workers in the informal aluminum foundry industry participated in this study. Aluminum in urine was measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Cognitive function was measured using the Montreal Cognitive Assessment-Indonesian version (MoCA-Ina) instrument. Results: A total of 69.6% of the subjects experienced cognitive impairment. There was a statistically significant relationship between urinary aluminum levels and cognitive impairment. Multivariate logistic regression analysis showed that urinary aluminum levels (adjusted odds ratio (aOR) = 6.550; 95% confidence interval (CI) = 1.281-33.499) and length of education (aOR = 16.885; 95% CI = 2.042 – 139.604) were associated with cognitive impairment, with cut-off value set at 45.985 µg/L. Other results showed that workers with less than 7 years of formal education have a 16.885 times higher risk of experiencing cognitive impairment. Conclusion: Workers with urinary aluminum levels ≥45.985µg/L and formal education fewer than 7 years have a higher risk of having cognitive impairment. Regular bio-monitoring of workers' urinary aluminum levels and adequate aluminum exposure control efforts are needed to prevent cognitive impairment in informal aluminum foundry workers.