While researchers have examined the effectiveness of various online gloss types on incidental L2 vocabulary learning, little research on online gloss languages has been conducted. Previous attempts which compared the effects of L1 and L2 glosses have reported mixed results. To fill the gaps, this study examined the effectiveness of Chinese and English e-glosses on incidental English vocabulary learning on a less-researched student group in CALL – junior high-school English-as-a-foreign-language (EFL) students. Seventy-eight students with Chinese as their first language read two online passages with either Chinese (L1) or English (L2) glosses. They were divided into four treatment groups: (1) high-proficiency students receiving L1 gloss before L2 gloss (n = 19), (2) high-proficiency students receiving L2 gloss before L1 gloss (n = 19), (3) low-proficiency students receiving L1 gloss before L2 gloss (n = 20), and (4) low-proficiency students receiving L2 gloss before L1 gloss (n = 20). After reading, the students were assessed with a vocabulary test which contained a definition-supply part and a cloze part serving as both post-tests and delayed post-tests. Repeated-measures analyses of variance were utilized to analyze the score data. Significant differences were found not only among the four groups but also between the two post-tests. Overall the high proficiency groups performed better in the post-tests, but the high proficiency group who received English glosses remembered more words in the delayed post-test than the high proficiency group who received Chinese glosses. The results show that as learners’ proficiency increases, they may be able to make better use of the L2 conceptual links for word retention and learning. The conclusions support the usefulness of both Chinese and English e-glosses which should be selected based on learners’ proficiency level.