A large body of research has been carried out on integrating picture dictionaries in EFL classes globally; however, a gap in the literature has been noticed on their effects at the tertiary level in the Iraq context. To address this issue, this paper, for the first time in the literature, focuses on the effects of the Oxford Picture Dictionary on 50 students' vocabulary expansion at a private university in Erbil, Iraq. Participants were determined through a simple random sampling method. A mixed methods research design was employed to collect data via a questionnaire, two vocabulary exams, and an interview. SPSS 26 and NVivo applications were used to analyze and categorize data accordingly. Quantitative data, via independent and paired samples t-test, revealed that experimental group students increased their marks significantly regarding vocabulary enhancement, while the progress was insignificant in the control group. Likewise, via content analysis, qualitative data unleashed that picture dictionary-enriched instruction sharpened learners' pronunciation, spelling, listening, reading, and speaking skills and drove them to learn more ambitiously. The outcomes indicated that picture dictionaries can be used effectively to reap their benefits in various aspects as supplementary material in main course lessons.