This study mainly examines the effect of Vocabulary Self-Collection Strategy (VSS) instruction on students' vocabulary knowledge. Moreover, it investigates the students' perceptions towards the implementation of VSS instruction. Thirty-eight Thai EFL undergraduate students majoring in English at a university located in Thailand participated in the study. To determine the students' vocabulary knowledge before and after the instruction, the vocabulary pretest and posttest were employed. A perception questionnaire and a semi-structured interview were conducted at the end of VSS instruction to elicit the students' perceptions towards VSS instruction. The paired samples t-test analysis indicates that the students improved short-term vocabulary retention, and they could retain vocabulary learned after VSS instruction. The results from the questionnaire and the semi-structured interview showed that they mostly agreed that VSS instruction assisted them in learning new words, memorizing word meaning, having a chance to choose their own words to learn, sharing words to classmates, working in a group, and realizing the importance of learning new words. The findings will help Thai EFL university students improve their vocabulary learning and generate an innovative body of knowledge regarding vocabulary instruction. Pedagogical implications are also suggested for EFL teachers who want to implement VSS in their vocabulary instruction.