This study investigated Iranian bilingual and trilingual EFL learners’ attitudes toward vocabulary learning strategies (VLSs) and examined differences in strategy use across proficiency levels. An explanatory mixed-methods design was employed to provide a comprehensive understanding of learners’ use of vocabulary strategies. In the quantitative phase, Schmitt’s (2000) Vocabulary Learning Strategies Questionnaire was administered to 160 learners, including 80 bilinguals and 80 trilinguals. Based on their performance on the Oxford Placement Test (OPT), participants were classified into four groups: high- and low-proficiency bilinguals and high- and low-proficiency trilinguals. In the qualitative phase, semi-structured interviews were conducted with 32 participants to further explore their attitudes and experiences. The results of Pearson correlation analysis indicated a significant relationship between vocabulary strategy use and English proficiency for both bilingual and trilingual learners. High-proficiency bilinguals and trilinguals reported frequent use of flashcards and repetitive exercises, whereas vocabulary learning software was the least frequently used strategy. In contrast, low-proficiency learners primarily relied on repetitive exercises and note-taking, while flashcards were used less frequently. Qualitative findings showed that high-proficiency bilingual learners demonstrated strong intrinsic motivation, employed a wide range of strategies, and held positive beliefs about interactive learning. Low-proficiency bilinguals, however, exhibited more extrinsic motivation, limited strategy use, and doubts about strategy effectiveness. High-proficiency trilingual learners reported combining traditional and modern strategies and expressed strong beliefs in the effectiveness of diverse strategies, while low-proficiency trilinguals reported restricted strategy use, extrinsic motivation, and challenges such as a lack of confidence.