Background <p>Infertility is a pervasive global health concern affecting millions of couples worldwide. Approximately 7% of the male population is infertile. Teratozoospermia, defined by &gt; 96% abnormal sperm morphology, is a major cause of infertility often linked to genetic defects. In our previous study, we identified three AGTPBP1 mutations (p.Glu423Asp, p.Pro631Leu, and p.Arg811His) in teratozoospermia cases. AGTPBP1 is a key enzyme involved in regulating tubulin polyglutamylation and generating Δ-2 tubulin, a major structural component of the sperm tail and an essential structure for sperm head differentiation. However, functional proof of the impact of AGTPBP1 Arg811His on sperm head and tail impairment remained unestablished.</p> Methods <p>Knock-in mice carrying the equivalent mutation, Arg791His (R791H) corresponding to the human mutation (R811H), in the <i>Agtpbp1</i> gene were generated and analyzed for sperm morphological abnormalities.</p> Results <p>Sperm morphological evaluation revealed a significant increase in the proportion of morphologically abnormal sperm in the <i>Agtpbp1</i>^{<i>R791H/R791H</i>} mice. Detailed morphological analysis revealed a significantly higher incidence of sperm head abnormalities and abnormal attachment of the head to the midpiece in the <i>Agtpbp1</i>^{<i>R791H/R791H</i>} mice relative to wild-type controls. Further, sperm with head defects from <i>Agtpbp1</i>^{<i>R791H/R791H</i>} mice exhibited abnormal accumulation of polyglutamylated tubulin within the sperm head. The mutant mice showed exactly the same morphological defects as seen in human patients and those displayed by mice lacking the complete carboxypeptidase A domain of AGTPBP1 but at a relatively lesser frequency.</p> Conclusions <p>We conclude that the R791H mutation in the <i>Agtpbp1</i> gene impairs sperm head and tail differentiation, resulting in sperm morphological defects.</p>