Abstract The aim of this research was to determine the relationship between internal motivation and academic achievement among high school students. Using multi-stage cluster sampling 307 high school students were selected. Then internal motivation questionnaire administrated. To measure the academic achievement, their academic grade average was used. Using the Pearson correlation coefficient, stepwise regression analysis, and Z test Collected data were analyzed. Results showed that there is positive and significant relationship between internal motivation and academic achievement. There is positive and significant relationship between interest, competence, effort, lack of stress, selection, value and academic achievement. Between components of the internal motivation, competence, lack of stress and value explained about 24 percent of student academic achievement variance. The relationship of internal motivation and academic achievement amongmale and female students is no different.