The coronavirus disease (COVID-19) pandemic has accelerated the transformation of educational institutions across the globe by implementing online and blended learning, which becomes an important aspect of the instruction and learning processes. The present study aimed to investigate the impact of both online and blended learning methods on grammatical knowledge and skill acquisition via an experimental approach. The study recruited 76 first-year medical learners to participate in an experiment for 7 weeks. Specifically, the experimental group studied the learning material face-to-face for 7 hours with 8 hours online, while the control group studied the same material online for 15 hours. The data were collected through pre-test and post-test. Although both approaches significantly improved learners' grammar performance, the study results discovered significantly higher learners' performance in a blended learning environment compared to solely online learning.