Teaching and learning in the 21st century is dealt with challenges and novelties. This study was conducted to investigate the relationship between 21st century skills, EFL learners' speaking and writing skills. The participants comprised 122 EFL learners from three private language institutes of Mashhad. Their selection was based on convenience sampling and the participation was entirely voluntary. The instruments used in this study consisted of 21st century skills questionnaire developed by Ashraf, Motallebzadeh, and Arabshahi (2014). Pearson's correlation coefficient, independent sample t-test, and structural equation modeling (SEM) were run to analyze the relationships among the 21st century skills components. Results of Structural Equation Modeling indicated that 21st century skills had a significant relationship with students writing and speaking. The interrelationship among five sub-constructs of 21st Century Skills Questionnaire (critical thinking and problem solving, communication and collaboration, interpersonal skills, leadership, and technology literacy) were analyzed on speaking and writing scores. Among five sub-constructs of 21st century skills questionnaire communication and collaboration had the highest correlation with foreign language speaking score and technology literacy had the highest correlation with foreign language writing score.