Despite the importance of reading literacy in adulthood, research in this field in Spanish-speaking countries is limited due to the lack of a valid tool to assess adults’ reading comprehension in their native language. Thus, we aimed to adapt the Deep Cloze test by Jensen and Elbro (2022) to Spanish and validate it. 453 undergraduate students from the universities of Valencia and Zaragoza completed the Spanish version of the Deep Cloze test. In addition, to test its criterion validity, subsets of the sample completed other text comprehension measures or provided their grades in introductory courses four months after completing the Deep Cloze test. Results indicated that while the Deep Cloze test has good internal consistency, correlations with other text comprehension measures and grades on a final exam are mostly small. The Deep Cloze fills an important gap by facilitating the assessment of reading comprehension efficiency in Spanish undergraduate students. This test presents important advantages, such as simplicity and administration time, and it can be used for research purposes. Finally, we discuss future research needed to test its validity to be used as a diagnostic tool to help deliver targeted support to struggling adult readers.