This study investigated the influence of academic staff OCB on the effectiveness of public universities in the state of Amhara. A concert-embedded mixed-methods (QUAN/qual) research approach was utilized. Sample universities and survey participants were selected through stratified and simple random sampling techniques. To gather quantitative data, validated questionnaires were distributed to survey participants, and data collected from 719 participants were analyzed using descriptive (mean, SD) and inferential (one-sample t-test, independent samples t-test, correlation, regression, and one-way ANOVA) statistical techniques. In contrast, qualitative data was gathered via semi-structured interviews and document analysis and analyzed thematically. The quantitative and qualitative findings indicated an above-average aggregate OCB and OE level. However, the qualitative analysis of OCB dimensions revealed mixed results: three components (conscientiousness, sportsmanship, and civic virtue) were found to be above average, while the other two (altruism and courtesy) were low. The study further demonstrated that academic staff members' civic virtue and courtesy behaviors were strongly and significantly associated with OE factors such as SOCI, SES, and SAD. Conscientiousness was above averagely associated with most OE dimensions but had a low correlation with SCD, SPD, and FS. Sportsmanship was weakly associated with all effectiveness factors, and altruism displayed a non-significant and negative relationship with all OE components. Regression analysis further revealed that civic virtue alone predicted 82% of the variance in OE, and when combined with courtesy, they predicted 87.8% of the variance. The analysis found no significant differences in OE based on academic staff demographic characteristics (sex, educational level, and experience). The findings indicate that while average OCB positively impacts OE it is insufficient for public universities aiming for long-term growth. Consequently, these institutions face significant risks in achieving their objectives. To enhance effectiveness, the institutions should focus on increasing employee compensation and fostering a positive organizational culture