The purpose of this study was to investigate Turkish and American undergraduate students' academic motivation and academic self-concept scores regarding the years that they spent in university. The analysis was based on 566 (284 Turkish, 282 American) undergraduate students where, Academic Motivation Scale and Academic Self-Concept Scale were used as measuring instruments. The results showed that there was a statistical significant effect of nationality and number of years spent in university on undergraduate students' intrinsic motivation, extrinsic motivation, and self-concept scores. Turkish students had higher intrinsic scores whereas American students had higher extrinsic scores and more positive academic-self concept compared to Turkish partners. Regarding grade level, senior students from both cultures had higher intrinsic motivation and academic self-concept scores compared to other grade levels. In terms of extrinsic motivation, there is steady decline in American students' scores as grade level increases. On the other hand, Turkish undergraduates' extrinsic scores decrease in the second year but increase in the third and fourth year of university education. Results were discussed by taking into consideration the social and cultural differences between two nations.