<p>The common marmoset (<i>Callithrix jacchus</i>) is a promising alternative model to the cynomolgus monkey owing to persistent supply shortages and cost inflation. Other practical advantages include its short lifespan, rapid sexual maturation, and small body size, reducing the amount of test items required. Here, we quantitatively assessed semen volume, sperm number, motility, morphology, testicular volume, and serum testosterone levels in eight adult male marmosets. Marmoset semen was collected by penile vibratory stimulation and analyzed. Results demonstrated considerable inter-individual variability, consistent with previous marmoset sperm analysis studies. Semen volume ranged from 6.00–52.33 μL, sperm number from 36.52–118.70 ×10⁶/mL, and serum testosterone from 447.95–9,982.40 ng/dL. Mean total and progressive motility were 83.04% and 72.21%, respectively, while sperm motility parameters were VCL 113.07 μm/s, VAP 91.29 μm/s, and VSL 67.86 μm/s. Morphological analysis revealed that 38.74% of sperm have normal morphology, with tail defects being predominantly detected. Testicular volume was also determined using ultrasonography and electronic calipers. This study provides a foundational dataset for future non-clinical developmental and reproductive toxicology (DART) studies, and underscores the importance of species-specific reference data and supports the broader regulatory application of the marmoset as a complementary non-human primate model in non-clinical DART studies.</p>