The main purpose of this study was to compare the impact of goal setting (GS), knowledge of results (KR), and combination of GS and KR on the extent of internal motivation level in learning of volleyball service by girl students. The total score of the participants were 96 individuals. In each experiment 48 participants were examined and on the basis of their adjusted scores they divided into 4 twelve groups. Pre and post tests were administrated after 2 and 10 days of practice for measuring the effectiveness of experimented intervention. The AAHPERD Volleyball Service Test, and internal motivation and personal data questionnaires were used in order to collect the data. To analysis the data in regard to acquisition and retention phases and to test the research hypotheses the factorial variation analysis and Toky followed up test were used .The findings show that in both experiment the main effects of sessions were statistically meaningful (F=21/27, P<0.001, F=10/27, p<0.001). We also found significant differences for the impact of internal motivation (F=41186, P=0/47). For the second retention tests (F=6/24, P=0.017) statistically significant differences were found. In summary, we can suggest that although the variability of internal motivation levels in some of the phases of the experiments were significantly meaningful, but in general we can claim that motivation strategies (goal-setting, KR) were not much effective in learning of volleyball service by the participants.