This study aims to analyze the effect of ball modification on learning outcomes of service under bolavoli. The research was conducted at SMPN 7 Kediri using quantitative methods. Data were collected through observation and measurement of students' lower service skills at pre-cycle, cycle 1, and cycle 2. The results showed a significant increase in the percentage of students who reached the criteria for completeness from 39% at pre-cycle to 84% at cycle 2. This increase indicates that the use of ball modifications, especially lightweight sponge balls, is effective in improving students' understanding and skills in the lower service technique of volleyball. Modification of tools in the form of a lightweight sponge ball as a substitute for a real volleyball, makes students more free, active, and more serious when learning the lower service in volleyball. This research supports previous findings which state that tool modification can increase students' enthusiasm and learning outcomes in physical education learning.