To facilitate teaching and learning vocabulary, this paper examines the effort and time spent on the direct instruction of lexical items in second language learning classes; whether it is a waste of time and learners should cope with it by themselves or it is acceptably effective in learning vocabulary. Hence, this study compared the effectiveness of two learning conditions: incidental learning through reading alone, and direct teaching of lexical items in context. ninty six participants, who were chosen after a pre-test, were taught in these two conditions. After teaching, four levels of word knowledge (form recall, meaning recall, form recognition, meaning recognition) were evaluated through four post-tests (form completion test, supply meaning and definition or translation test, selection of the correct form test, selection of the correct meaning test). To assess retention of target words over time, this post-test was administered twice; once immediately after the instruction, and once again one week after the instruction. The descriptive analysis of results showed that direct instruction in context is more effective than incidental learning alone in all four levels of word knowledge acquisition. The findings of the present research emphasize the balanced application of both direct and incidental learning approaches. It, also, demonstrates the value of the effort and time spent for direct instruction in second language learning classes.