Studies on listening comprehension have increasingly used Computerized Dynamic Assessment (CDA), a new strand of Vygotsky’s dynamic assessment. This study investigated whether English as a foreign language (EFL) learners’ responsiveness to CDA mediation significantly enhanced their inferential skills in multiple-choice listening comprehension tests. Moreover, it examined the role of guess-checking items in reducing the guessing effect. A sample of 94 Iranian EFL university students of B2 proficiency level (38 male and 56 female) was recruited through purposeful sampling. The researchers designed and operated CDA software delivered through a dedicated website, www.lingeli.com, to assess EFL inferential listening comprehension skills. The quantitative data obtained from the participant’s performance in the pretest and the mediation stage were analyzed using SPSS. Two paired-sample T-tests were run to compare EFL learners’ mediated and actual scores to explore the development of their inferential listening and compare the actual scores of learners with and without calculating guessing effect scores, respectively. The results showed that learners’ responsiveness to mediation significantly changed their performance on the CDA of inferential listening skills. Additionally, adding guess-checking items significantly decreased the impact of guessing in the CDA multiple-choice tests, which provided the opportunity to obtain a more comprehensive picture of learners’ abilities. The findings offered more insights into the effective role of CDA in improving EFL learners’ inferential listening comprehension skills. They called for implementing CDA programs to diagnose learners’ deficiencies and strengths and uncover their zone of proximal development.