Broodstocks of cobia, Rachycentron canadum, were fed raw fish (RF) or three formulated diets of similar proximate composition but different n-3 highly unsaturated fatty acid (HUFA) levels: 0.94% (D1), 1.31% (D2), or 1.72% (D3) of the dry weight (dw). Egg fatty acid composition was significantly different between dietary groups and reflected that of the diets. The total n-3 HUFA and especially docosahexaenoic acid contents in eggs of groups fed formulated diets were significantly lower than in group fed RF, whereas the egg content of arachidonic acid (ARA) in groups fed Diets D2 and D3 were significantly higher than in groups fed Diets D1 and RF (P < 0.05). Although no significant differences in spawning quality were found among dietary groups (P > 0.05), a tendency of better spawning performance was observed in the group fed RF (1.86% n-3 HUFA of dw). A tendency of lower fertilization success was associated with groups that had higher egg content of ARA (D2 and D3). Results of this study suggest that cobia broodstock requirements of dietary n-3 HUFA should be higher than 1.86% dw and that high dietary levels of ARA (0.42–0.60% dw) may affect cobia fertilization success negatively.