This study investigated the relationship of acrosome reactions and fatty acid composition on fertility in boar sperm. The acrosome reaction of sperm was induced via methyl-beta-cyclodextrin (MBCD), and acrosome reaction, plasma membrane integrity, and fertility were analyzed. The fatty acid composition of the excess acrosome reacted sperm was determined via gas chromatography. The results showed that the acrosome reaction in sperm was induced over 85% of the time by 60 mM MBCD treatment, and the plasma membrane integrity was significantly decreased and was dependent on the MBCD level. The acrosome reacted sperm resulted in significantly higher saturated fatty acids (SFAs) and lower unsaturated fatty acids (PUFAs) than the non-acrosome reaction group. Moreover, the acrosome reacted sperm from 60 mM MBCD significantly decreased in vitro fertility and blastocyst formation relative to non-acrosome reacted sperm, and the acrosome reaction was positively correlated with SFAs and negatively correlated with PUFAs. Of these fatty acids, C22:5n-6 (docosapentaenoic acid [DPA]) and C22:6n-3 (docosahexaenoic acid [DHA]) were directly negatively correlated with the acrosome reaction (r = -0.982 and -0.947, respectively). In conclusion, the excessive acrosome reactions may occur by reducing the PUFAs, which may then dramatically decrease sperm fertility in pigs.