The primary objective of this study was to evaluate the impact of explicit instruction aimed at improving vocabulary on the writing proficiency and long-term retention of new vocabulary among second language (L2) learners. The achievement was accomplished through the administration of a fill-in-the-blank assessment, which included 30 individual words and 6 lexical phrases, to a group of 30 EFL students at an upper-intermediate level. Subsequently, these students engaged in a reading exercise centered around the topic of 'Bull Fighting' and subsequently crafted a paper titled 'A Cruel Sport'. The results demonstrated a notable enhancement in the quantity of terms actively utilized in their writing following the focused vocabulary teaching. The statistical analysis revealed that the participants were capable of retaining the newly-acquired language even after a considerable amount of time had elapsed since the lesson. This study presents comprehensive information on these findings and provides suggestions for L2 teachers, asserting that although comprehending a word does not inherently result in its active utilization, learners possess the capacity to enhance their active vocabulary and accurately employ recently acquired words. Explicit training in vocabulary is advantageous for converting recognition vocabulary into productive language during immediate writing tasks and enhancing retention. Nevertheless, consistent and regular practice in utilizing recently learned vocabulary is necessary for it to become effective in long-term written expression. Manuscript profile