This study was conducted to examine the possibility of reducing PCR reaction volume of the PowerPlex Fusion system to produce full DNA genotyping of some forensic casework samples. Human DNA profiling was analyzed by half and quarter PCR reaction volume of the PowerPlex® Fusion system amplification kit to examine the reliability of the obtained STR profiles. Serial DNA dilutions (1 ng, 0.5 ng, 0.125 ng, 0.0625 ng) of a buccal swab were used with half PCR reaction volume to analyze STR loci via estimating their peak height and stutter ratio. The peak height ratio was above 60% in all heterozygous loci obtained and the best ratio of stutter was in the sample with a concentration of 0.0125, as it was less than 16% in all loci. Half and quarter PCR reaction volumes were evaluated by different casework samples (blood, hairs, and nails). The results showed that half reaction volumes gave 100% STR profiles of blood and nail samples and 60% of hair samples gave complete profiles. In 40% of hair samples, alleles were dropped out in the loci Penta E and Penta D. Quarter PCR reaction volumes gave 30% of blood and hair samples and 20% of nail samples produced a complete STR profile. It was possible to reduce the PCR reaction volume by more than half while still obtaining a complete STR profile suitable for human identification, despite some negative results that may have been due to DNA purity issues. Further studies are necessary to generalize this conclusion.