Abstract This study employed eye-tracking technology to examine how English as a foreign language learners at different proficiency levels process L1-glossed words and how this processing relates to L2 reading comprehension. Forty-seven university students were divided into a higher-proficiency group (n = 23) and a lower-proficiency group (n = 24) based on their L2 proficiency. Both groups were asked to read an English passage with L1 (Chinese) glosses. Their eye movements were recorded with an eye-tracker as they read. After reading, they were immediately given a reading comprehension test. Analyses of the eye-tracking data showed that the higher-proficiency L2 learners spent more time on unfamiliar words than the lower-proficiency L2 learners. Furthermore, lower-proficiency L2 learners’ longer processing time on glossed unfamiliar words was related to their higher reading comprehension scores, whereas this relationship was not found in the higher-proficiency group. These results revealed that the contribution of L1 glosses to L2 reading comprehension performance varied across L2 learners’ proficiency levels. Our findings have important implications for second language instruction.