The main objective of this study was to elucidate whether there are any effects of sperm dilution time before short-term storage in common carp. The sperm of five males (2-2.5 kg body weight, 3 years old) with good spermatozoa motility (˃90 %) were diluted with carp extender immediately, 3 h post-diluted, and undiluted fresh sperm was used as control. Sperm motility and velocity of undiluted and diluted sperm were evaluated using a CASA system. A two-way ANOVA revealed that spermatozoa motility, curvilinear velocity (VCL), and straight-line velocity (VSL) were significantly impacted by storage time, varying dilution with extenders, and their interaction (p <
0.001). Sperm motility and velocity dropped steadily with increasing storage periods for diluted sperm, while they drastically fell for undiluted sperm and became immotile at 5 days post-storage. In the control group, the mean percentage of sperm motility was achieved by 40.60 % at 3 days post-storage and sperm diluted with Cejko solution immediately and 3 h post-diluted sperm retained motility at 65.13 % and 65.63 %, respectively, at 3 days post-storage and retained motility of 39.45 and 40.43 %, respectively, at 7 days post-storage. After 7 days post-storage, the diluted (immediately and 3 h post-diluted) pooled sperm had a 61.01 % and 56.70 % fertilization and a 43.40 % and 36.52 % hatching rate, whereas fresh sperm had an 89.34 % fertilization and 78.06 % hatching success. According to the results of the fertilization and hatching assay, compared to fresh sperm, 7 days of stored diluted pooled sperm produced a 68.29 % fertilization rate and a 55.60 % hatching rate.