In educational psychology, mindsets refer to a set of core beliefs about intelligence and its role in successful learning in a specific domain. This study investigated the extent to which, the EFL learners’ mindsets might predict their English achievement considering the mediating roles of engagement and self-regulation. The data were collected by means of three questionnaires: The Language Mindset Inventory (LMI), the University Student Engagement Inventory (USEI), and the Academic Self-Regulated Learning Scale (A-SRL-S), as well as the institutes’ reports on their English achievement. We analyzed the data quantitatively using the SPSS 20 and Amos 8 Software. The results revealed that there was a significant direct relationship between language mindsets and English achievement of the EFL learners. Besides, this relationship was significantly mediated by the learners’ engagement and self-regulation. Drawing on the findings of this research, the challenge for teachers is to cultivate in students the mindsets that emphasize growth and potentials rather than constraints and stagnation.