This study examined the comparative impacts of convergent and divergent tasks while employing critical thinking techniques on EFL learners’ writing. Accordingly, 60 male and female learners were chosen from a group of 90 learners based on their scores on a sample PET previously piloted in one of Tehran’s language schools. The learners were then randomly put into two experimental groups: 30 learners undergoing convergent tasks and 30 learners receiving divergent tasks. Both groups were exposed to critical thinking techniques. After the treatment, a sample PET writing section was administered as the posttest to both groups with their mean scores being compared; the results showed that neither group outperformed the other significantly. This result probably indicates that the critical thinking instruction was more of an influential factor compared to the variability of convergent and divergent tasks, thereby consolidating further the notion that critical thinking instruction is a highly influential factor in ELT. Manuscript profile