This study aimed to examine the direct and indirect effects of arm muscle strength, hand–eye coordination, and concentration on underhand passing performance in junior volleyball athletes. A quantitative approach with path analysis was applied involving 30 male athletes from a school volleyball team using total sampling. Arm muscle strength was measured using the push-up test, hand–eye coordination using the wall toss test, concentration using the concentration grid test, and passing performance using a standardized underhand passing test. The results showed that arm muscle strength (β = 0.548), hand–eye coordination (β = 0.376), and concentration (β = 0.177) had significant direct effects on passing performance (p < 0.05). Indirect effects through concentration were also identified, although relatively small. The model explained 90.4% of the variance in passing performance. These findings indicate that underhand passing is influenced by physical, motor, and cognitive factors, highlighting the importance of integrated training approaches in volleyball development.