This study compared the multidimensional effects of written and oral vocabulary exercises on EFL learners' retention of single-word items (SWI) and multi-word items (MWI). Two teaching experiments (times) were conducted with 54 college students, who studied four themed-based texts, two at a time. A total of 60 unfamiliar vocabulary items, 30 in each experiment, were tested in four dimensions one week after the treatment. Hierarchical linear modeling (HLM) was performed to analyze the data. The results showed that all four fixed variables (times, vocabulary exercises, vocabulary dimensions, and types of vocabulary items) had significant effects on students' retention of SWI and MWI. Overall, students performed better at Time 1 for doing the written exercises; students scored highest for L2 meaning recall, followed by aural form recall, aural meaning recall, and L2 form recall. Students consistently performed better on the MWI than on SWI. Regardless of whether students scored higher on written exercises, a short questionnaire indicated that they perceived oral exercises interesting and helpful. Class discussion revealed that students enjoyed learning MWIs that comprised of familiar words, and various strategies were applied to acquire the MWIs. Pedagogical implications of the results were discussed.