This experimental quantitative study explored the effects of an integrated vocabulary instruction on reading comprehension performance of A1 EFL learners in a rural public school in Ecuador. The participants of this study were students between 15 and 17 years old in their first baccalaureate year, all of them were selected by convenience sampling. The participants were divided into two groups (traditional and integrated) and asked to participate in eight reading lessons with their designated vocabulary instruction. After each class, they took part in a reading comprehension test based on literal comprehension questions. Moreover, the perceptions from the experimental group were gathered by a questionnaire. Additionally, a vocabulary knowledge scale (VKS) was used three times to measure previous knowledge, learning, and retention of words. This study shows that an integrated vocabulary instruction improves learners' reading comprehension, and it is beneficial for vocabulary learning and retention. Furthermore, this research work proposes a further study on the benefits of an integrated instruction by working with upper levels of proficiency.