The paper reports a small-scale exploratory research on the effectiveness of blended learning on EFL learners’ mastery of vocabulary. It aims (1) to determine the effectiveness of blended learning in vocabulary lessons, and (2) to identify the respondents’ opinions about the blended learning experience. An intact class of 21 students was taught vocabulary lessons, which amounted to 100 minutes of class time every week. The lesson focused primarily on intentional learning, with receptive recall of words as the main objective. In addition to this regular intentional learning, they were instructed to read authentic materials and utilize a vocabulary profiler to obtain a vocabulary profile of the materials. They were taught how to interpret the results of the profiling. Next, they were asked to show their texts on a blog so as to allow their classmates to learn new words from the texts. Questionnaires were used to elicit their opinions on this teaching technique. At the end of the 16-week semester a post-test was administered to determine the gains in their vocabulary mastery. While there was an apparent gain in their command of 5000-level English words, they did not make a similarly encouraging achievement in the new words from the texts. An explanation that accounts for the finding was offered. Meanwhile, the answers from the questionnaires seemed to reflect their positive attitude toward the use of authentic materials in this fashion.