This study investigated the effect of Narrow Reading (NR) on learning mid-frequency words. Vocabulary Size Test (VST) designed by Nation and Beglar (2007) was administered as the first pre-test to 196 students, from among whom 91 students whose vocabulary size ranged between 2100- 3500-word families, , became the target of this study and were randomly classified into four groups. Then another pretest administered was a modified version of Wesche and Paribakht’s Vocabulary Knowledge Scale (VKS) which assessed how well they knew twenty vocabularies derived from the expository and narrative texts. After thirty sessions for direct instruction, VKS was repeated immediately as a posttest to assess vocabulary learning while a month later, VKS was taken as a delayed posttest to assess vocabulary retention. To address research questions, a mixed design factorial ANOVA was conducted. The findings revealed that while the theme was fixed, reading expository texts rather than narrative ones led to the growth in vocabulary knowledge. In addition, the group that read narratives forgot most of the mid-frequency words in the retention phase. As opposed to multi-author texts, reading texts written by one author resulted in a better vocabulary achievement in both learning and retention phases. It was also revealed that there was no interaction between genre and author. In other words, the author was as influential in learning mid-frequency words among expository texts as it was in narrative ones. Finally, it was concluded that NR has a positive effect on learning mid-frequency words.
