The aims of this study were to show the existence of individual differences in the distribution of sperm acrosome-associated 1 (SPACA1) among male patients of infertile couples and to examine their possible impact on the outcomes of conventional in vitro fertilization (IVF). The spermatozoa were collected from male patients of infertile couples, washed by centrifugation, collected by the swim-up method, and then used for clinical treatments of conventional IVF. The surplus sperm samples were fixed and stained with an anti-SPACA1 polyclonal antibody for the immunocytochemistry. In the clinical IVF treatments, fertilization rates and blastocyst development rates were evaluated. The immunocytochemical observations revealed that SPACA1 were localized definitely in the acrosomal equatorial segment and variedly in the acrosomal principal segment. Specifically, the detection patterns of SPACA1 in the acrosomal principal segment could be classified into three categories: (A) strong, (B) intermediate or faint, and (C) almost no immunofluorescence. The SPACA1 indexes were largely different among male patients with the wide range from 13 to 199 points. The SPACA1 indexes were significantly correlated with developmental rates of embryos to blastocysts (r = 0.829, P = 0.00162), although they were barely associated with fertilization rates at 19 h after insemination (r = 0.289, P = 0.389). These results suggest that the distribution of SPACA1 in sperm affects the outcomes of conventional IVF. In conclusion, this study provides initial data to promote large-scale clinical investigation to demonstrate that the SPACA1 indexes are valid as molecular biomarkers that can predict the effectiveness of conventional IVF of infertile couples.