This study aimed to analyze the effect of game-based learning (GBL) through the use of Genially in English as a foreign language (EFL) online instruction. The participants were 61 EFL undergraduate students, who were distributed into an experimental group (32 students), and a control group (29 students). Their ages ranged from 22 to 56 years old, and their English proficiency level was B1, according to the Common European Framework of References (CEFR). The students were enrolled in two pre-intermediate courses that are part of an EFL Teaching program at a private university in southern Ecuador. The courses were delivered in an online remote learning environment due to the COVID-19 pandemic. The study followed a quasi-experimental approach and it took place over a sixteen-week period. The instruments included a diagnostic survey, a pre-test, a post-test, a students’ perceptions survey, and a semi-structured interview. The main findings revealed that Genially games have the potential to enhance EFL learners’ academic performance in online instruction, particularly in aspects related to students’ knowledge of grammar and vocabulary in context. Besides, it was found that according to students’ perceptions, the implementation of games based on their real learning needs increases their motivation, especially when feedback is effectively provided.