Intensive English programs are courses in which students participate in a higher number of classes in a shorter period. The available literature on intensive English courses indicates inconsistent results necessitating further research in this area. This study investigated the effect of an intensive English program on a group of Malaysian Secondary School students (n = 30) following a single group quasi-experimental design. Paired samples t-test was used to analyze the students' scores before and after the treatment that lasted four weeks. The results indicated that the students scored significantly higher (p = 0.000 <0.05) at post-test. The study has useful implications for English as a Second Language (ESL) teachers, researchers, and curriculum developers. Further research is required before the findings of the study can be generalized.