This study investigates the effects of first language (L1) and second language (L2) hypertext glosses on reading comprehension (RC), immediate vocabulary recognition (IVR), and delayed vocabulary retention (DVR). A group of 83 secondary school low-achieving students (10th grade) were assigned to read glossed texts, L1 and L2 hypertext glosses. This study may help teachers create glossed texts to improve students' incidental vocabulary learning and it can contribute to the raising of students' attitudes towards learning English with encouraging and interesting vocabulary learning conditions. A repeated measure t-test design (without control group) was employed. The results indicated that the effects between the L1 and L2 glosses were significantly different. The paired sample t-test revealed that the L1 gloss scores were significantly higher than the L2 gloss scores regarding RC (p = 0.014), IVR (p = 0.000) and DVR (p = 0.000). The pedagogical implications suggest that reading with the assistance of glosses can be successfully integrated into a real classroom setting to improve low-achieving students' vocabulary knowledge in an English as a Foreign Language (EFL) context. It is recommended that future studies use L1 written story retelling/recall techniques to collect the reading comprehension and vocabulary retention data as choices offer random guesses to the participants.