This study investigated the relationship between foreign language motivation and self-determined motivation, as well as the issue of students' perceptions of strategies used to improve foreign language motivation and achievement among undergraduate students in the department of foreign language. This research was conducted in two mid-western universities among undergraduate foreign language learners. The participants were undergraduate foreign language learners. A total of 391 students from 18-43 years old started the paper-and-pencil surveys in which they shared their views and perceptions about foreign language learning motivations and strategies to improve motivations and achievement. However, only 380 completed the majority of all sections. The study began on January 2, 2018 and concluded on February 5, 2018. All data were analyzed using Statistical Package for the Social Sciences (SPSS) version 24.0, through which descriptive statistics were conducted to see normality among the variables. Correlations and regressions were conducted to examine the effects of each variable on students' perceived success in a foreign language learning. The results of the study indicated that autonomy and competence predicted students' intrinsic motivation and perceived success in learning a foreign language. The study also demonstrated that there were relationships between integrative and instrumental motivation with intrinsic and extrinsic motivation. Also, the emotional control improved students' motivation and perceived success in learning a foreign language. The autonomy competence, and integrative motivation contributed a significant amount of variance in students' perceived success. Finally, the fear of speaking in a foreign language predicted students' motivation and academic success. The results strongly suggested that promoting self-determined motivation was an avenue to attaining success in foreign language learning, and teachers could improve students' motivation by supporting their basic psychological needs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]