This descriptive study aimed at investigating the guessing words-in-context strategies of six beginning and six upper-intermediate level EFL students at the Faculty of Engineering and Architecture, Osmangazi University. The data were collected through individual think-aloud protocols (TAPs) and retrospective sessions (RSs). In the TAPs, the participants were told to think aloud while they were guessing the five test words. In the RSs, the participants later reported what helped them in their guessing. One of the major results revealed from the analyses of TAP and RS transcriptions showed that the beginning level participants used guessing words-in-context strategies more frequently than the upper-intermediate level participants although both groups frequently used the same strategies which were contextual clues and translation. Another finding illustrated that the use of guessing words-in-context strategies varied according to the clues that the test words offered rather than the proficiency level of the students. The results of the study suggest that morphological clues, phonological structure of an unknown word, as well as the contextual richness of the passage with the unknown word, determine the types and frequencies of guessing words-in-context strategies.