This study investigates the relationship between depth of academic vocabulary knowledge and academic success among Saudi English-as-a-foreign-language university students. Fifty fourth-year university students majoring in English completed a vocabulary depth test, the Word Associates Test (WAT), based on the Academic Word List (AWL). Then, students' grade point averages (GPAs) were obtained as a measure of academic success. Furthermore, a vocabulary learning strategy (VLS) questionnaire was administered to explore the students' use of various VLSs. In addition, two focus group discussions were conducted to elicit participants' views and experiences of English vocabulary learning. The scores on the WAT were positively correlated (r = 0.407, p < 0.01) with GPA. Results of the regression analysis show that the WAT scores accounted for 16.6% of the variance in GPA. Analysis of the data on VLSs reveals that the participants were medium-level VLS users who employed metacognitive strategies most frequently. Strategies that involve focused intentional vocabulary learning, such as learning from word cards and wordlists, were reported to be used the least. Results of the present depth study support previous findings of vocabulary breadth studies on the high predictive power of academic vocabulary knowledge in relation to academic success. Implications of the results for academic vocabulary teaching and learning are considered.