Triploid induction is a promising tool for sterility and triploid turbot showed improvement in growth after sexual maturation. However, it is essential to characterise the response of triploids to pathogens to evaluate their suitability to aquaculture. The aim of the study was to investigate the ploidy status of turbot on the innate immune response and susceptibility against Vibrio anguillarum, Aeromonas salmonicida, and viral haemorrhagic septicaemia virus (VHSV) infection. Diploid and triploid turbot were subjected to experimental infection with these pathogens via intraperitoneal (IP) injection and immersion. Antibody response against V. anguillarum and A. salmonicida was assessed at 0, 7, 14, 21, and 30 days post injection. A. salmonicida did not cause any mortality in ploidy groups. However, ploidy had significant effects on susceptibility against V. anguillarum and VHSV infections. Triploids were significantly more susceptible to both V. anguillarum and VHSV. While there were no significant difference in antibody response against V. anguillarum in ploidy groups, antibody response of diploid turbot against VHSV was significantly higher.