The present study investigates whether textual enhancement had any effects on grammar learning (tag questions) and reading comprehension, and whether the types of tag question contributed to the benefits of textual enhancement. The study employed a pretest--posttest design with three treatment sessions. The target forms were English tag questions, which were grouped into three types: auxiliary (AUX), do-support (DO), and modal (MODAL). Participants were 69 Japanese high school students, who were assigned into three experimental groups (n = 52) and a control group (n = 17). The control group received unenhanced passages, whereas three experimental groups received passages, each of which included one of the target forms visually manipulated. To examine the effects of textual enhancement, the participants performed a multiple-choice grammar task consisting of 18 items. Reading comprehension was assessed using a 10-item multiple-choice test based on information from the passage. The results showed (1) that the effectiveness of textual enhancement on learning the target forms appeared in one enhanced group (Group 3) but it did not appear in the other two groups; (2) that textual enhancement did not detract from reading comprehension; and (3) that enhancing specific types of the target forms seemed to facilitate Group 3's learning, but did not have any effects for the other groups.