Strengthening the core muscles is a significant component in minimizing sports injuries, speeding up rehabilitation, and boosting application of technical skills and physical abilities. The purpose of this study was to investigate the effect of core strength training on passing technical skills and selected physical fitness qualities. The study employed an experimental research design. The target population of this study were male volleyball trainees of Bahir Dar University (N=22) with the age of (EG=14.82±0.751, CG =15.00±0.775) were participated by using comprehensive sampling technique and randomly assigned into two equal groups. Both the experimental group (EG, n = 11) and control group (CG, n = 11) participated in the regular volleyball training, but only EG performed additional core strength training for 10 weeks, with 3 sessions per week, each lasting 40 to 60 minutes. Subjects were measured on forearm passing accuracy, overhead passing skill, muscular endurance, explosive power and flexibility on two occasions, first before administration of core strength training as pre-test and after 10 weeks of the training as post-test. The data collected from the study subject was analyzed using SPSS version 26 software by ANCOVA to compare between groups post tests and to observe the effect sizes of core strength training on passing performance and physical fitness qualities at 0.05 level of significant. The results showed that core strength training had large effect size and significantly improved forearm passing accuracy, overhead passing skill, muscular endurance, explosive power and flexibility in EG at (P<0.05). However, no significant improvements were found in all the variables in CG (P>0.05). Based on this finding, it can be concluded that core strength training has significant effect on improvement of passing performance and physical fitness qualities of volleyball players. Therefore, this type of training method is suggested to volleyball players and coaches to include in their training sessions for improvement of passing technical skills and physical fitness qualities.