<p>Recent years have witnessed a surge in reports of <i>Aeromonas caviae</i> infections among aquatic species, posing a significant challenge to the aquaculture industry. To address this issue, this study investigated the impact of four distinct adjuvants on the efficacy of an inactivated vaccine against <i>Aeromonas caviae</i> AC-CY in crucian carp (<i>Carassius auratus</i>). We evaluated the adjuvant properties of aluminum hydroxide (Al (OH)₃), glucan, astragalus polysaccharide (APS), and propolis by formulating them into 1:1 adjuvanted inactivated vaccines. For comparison, we included a blank control group and a group administered with the inactivated vaccine alone. To assess the immunological response, we collected blood and tissue samples from the different groups and analyzed various immune-related parameters, including serum biochemical indices, antibody titer, leukocyte phagocytosis activity, and cytokine expression in various tissues. Our findings revealed that inactivated vaccination conferred an immunological protective effect on crucian carp. Notably, all four adjuvants enhanced the immunity and resistance of the fish against <i>A. caviae</i> AC-CY infection, with astragalus and propolis demonstrating the most pronounced overall immune response, including highly significant (<i>p</i> &lt; 0.001) upregulation of key cytokine expression in multiple tissues compared to controls. After careful consideration, astragalus (APS) was identified as the optimal vaccine adjuvant, conferring the highest relative percentage survival (RPS) of 84% upon challenge. In summary, this study provides valuable insights into the selection of adjuvants for <i>A. caviae</i> inactivated vaccines, highlighting the potential of APS as a safe and effective adjuvant for large-scale production.</p>