<p>English language proficiency is essential for academic and career prospects of individuals who speak English as a second language (ESL). Yet, gaining English proficiency is a difficult task for ESL learners, particularly adults who may not have acquired the language in their formative stages. Gamification helps to bridge the gap by making language learning enjoyable. But there is no clear understanding of which strategy works best for ESL adult learners between personalized (individual-based) and collaborative (group-based) gamification. To address this gap, this study presents a systematic synthesis of the literature on gamified vocabulary learning among adult ESL learners. This review included 19 articles published between January 2015 and December 2024. The findings show that gamification, irrespective of whether it is personalized or group-oriented, has beneficial impacts on language learning, engagement, and motivation. Individual-based gamification promotes learner autonomy while collaborative learning encourages social interaction. Both strategies work for the benefit of learners’ academic achievement, motivation, and engagement. Learning contexts seemed to influence the success of these strategies. The findings indicate that teachers have to weigh the contexts of their ESL classrooms in the design of gamification strategies.</p>