Becoming one of six official United Nations languages, English proficiency has become a prominent requirement for students and professionals entering international education and/ or careers, as assessed through standardized English proficiency tests. English learners conducted varied procedures to pursue the minimum test score criteria, including joining an English test preparation program. This study investigates the effect of English test preparation as an intervention on EFL learners' English language proficiency performance by reviewing the effect sizes found by previous studies using meta-analysis of pre-post contrasts. A total of 20 selected studies, according to the criteria determined by researchers between 2018-2021 and conducted in various countries, were collected from Google Scholar sources and included in the research. English language proficiency performance, as indicated by their test scores, is independent of the language skills tested with a p-value of less than 0.05 (p-value = 0.00) and an average weighted effect (M) that appears to be 0.859. This research implies that adequate test preparation is essential for English language learners who wish to achieve the desired level of proficiency. Apart from the ability to write, speak, and read, the psychological aspects of students are also important to prepare before they take the intended test.