Low serum alanine aminotransferase activity and high aspartate aminotransferase (AST)/ALT ratio may be associated with high mortality in older people. We aimed to confirm this in an 8-year retrospective cohort study. Clinical data for 5,958 people aged 67–104 years were analyzed for their relationships with all-cause mortality using artificial intelligence (AI; Prediction One [Sony Network Communications Inc.]) and conventional statistical analysis (SAS Enterprise Guide [SAS Institute Inc.]). In total, 1,413 (23.7%) participants died during the study. Auto-AI analysis with five rounds of cross-validation showed that AST/ALT ratio was the third largest contributor to mortality, following age and sex. Serum albumin concentration and body mass index were the fourth and fifth largest contributors, and the individual serum ALT and AST activities were the seventh and tenth largest contributors. Conventional survival analysis showed that ALT, AST, and AST/ALT ratio as continuous variables were all associated with mortality (adjusted hazard ratios (95% confidence intervals): 0.98 (0.97–0.99), 1.02 (1.02–1.03), 1.46 (1.32–1.62), respectively; all p <0.0001). In conclusion, both AI and conventional analysis suggest that of the conventional biochemical markers, high AST/ALT ratio is most closely associated with all-cause mortality in older people.