Since the 1970s, the TOEFL has been a mandatory English proficiency test that non-native English speaking students had to take to demonstrate their language proficiency to attend U.S. colleges and universities (Educational Testing Service, 2011). The current study addressed this gap in literature by examining the relationship between Chinese international students’ TOEFL scores and their academic success as measured by their overall Grade Point Average (GPA). Using Astin’s Input-Environment-Outcomes (I-E-O) model as the theoretical framework, the roles of other Input and Environment factors that may impact Chinese international students’ GPA, independently from TOEFL, were also investigated. An explanatory mixed-methods approach was used. Through snowball sampling 201 survey participants were recruited, and interviews were conducted with a subsample of seven students. A Pearson correlation analysis found a moderate positive correlation between TOEFL score and GPA (r = .30, p < .001). An HLM analysis revealed that Input factors (Years Living in the U.S., Institution, Major) explained 7.7% of the variance in students’ GPA. Environment variables (Self-Confidence, Study Habit) explained an additional 11.5%, when controlling for Input factors. Thus, a total of 19% of the variation in GPA was explained by Input and Environment factors alone. HLM analysis revealed that the TOEFL score was the strongest factor predicting GPA, but only explains 6.9% of the total variation. Qualitative analysis of themes showed that “language barrier” and “cultural adjustment” are two main factors influencing the experiences of Chinese international students’ academic success in the U.S. in their perspective.