Carried out in an explanatory sequential design, the current research examined the effect of Duolingo on the language learning achievement and self-regulated learning of Iranian language students. To conduct this study, a sample of 50 Iranian college students was recruited. The participants were college students at the University of Kurdistan, Iran. They included both males and females whose ages ranged from 18 to 22 years old. They were required to pass some French courses to get their bachelor’s degree. They were randomly assigned to both the experimental group (n=25) and the control group (n=25). Through one university semester, 16 sessions, in addition to traditional course content, the control group was provided with pdf files of Duolingo content, whereas, the experimental group had to engage with Duolingo as a complementary device outside of the class. As well as the data collected from Duolingo for schools, a self-regulated questionnaire, and a semi- structured interview were implemented. ANCOVA analysis and independent sample t-test were implemented to analyze the quantitative data as well as the content analysis (also called thematic analysis) which was carried out to analyze the qualitative data of research. The findings of this study showed that Duolingo can significantly impact both language achievement and self-regulation of learners. This elucidated the fact that Duolingo is a beneficial app for teaching French to beginner students.