In this study, the effects of web-based, gamified vocabulary instruction (through Quizlet’s Match activity and online leaderboards) on assessment scores and student motivation are examined. The primary features of gamification present in this study include ‘conditions for victory’ and leaderboards. Japanese English language learners from two online Listening and Speaking courses at Kyushu Sangyo University took part in this experimental study. The control and experimental groups initially received identical vocabulary instruction, and in week 8, both classes took a vocabulary recall assessment (75 words). Afterwards, gamified vocabulary instruction (via the Quizlet application’s Match game) was introduced only to Class B (the experimental group). At the end of the semester, a second vocabulary recall assessment was administered to both classes (75 new words). Previous studies have claimed that gamified instruction increases a learner’s motivation to (a) study a second language and (b) study second language vocabulary. Results of the final assessment indicate that gamified vocabulary instruction through Quizlet’s competitive Match game and the use of a public leaderboard have a positive effect on vocabulary assessment scores. However, quantitative student feedback from this study suggests this manner of gamified instruction may not affect Japanese English Language Learner’s (ELL) motivation to study English or English vocabulary.