The current study aimed at using a deliberation-based strategy for enhancing the 21st century skills of EFL pre-master candidates (n=6), since such participants can contribute much to their teaching career. Besides, they are more able to disseminate the 21st century culture among their learners. The study was quasi-experimental of pre/post one group design. The literature review presented a theoretical background on deliberation, the relationship between deliberation, the 21st century skills and EFL education, and why deliberation is specifically for developing the 4 C's: communication, critical thinking, collaborative dialog and creativity. This helped to identify the rationale of the study and its aims. Besides, it helped to well select the issues/problems for practicing deliberation, and the activities to be used and above all the sequence of the strategy proposed. The study instruments were 4 tests for the 4C's, which were pre/post administered to the study participants. Means, standard deviations, T-tests, and effect sizes were computed to verify whether the study questions were answered. The study results indicate that the deliberation-based strategy was effective in developing the participants' 21st century skills. The results seem trustworthy and generalizable due to the close relationship discovered in the result interpretation between deliberation and the 21st century skills.