The present study aimed to explore how tolerant of ambiguity Iranian EFL learners at university level are and if gender plays a role in this regard. To this end, upon filling in the revised SLTAS scale of ambiguity tolerance 194 male and female Iranian teacher trainees were assigned to three ambiguity tolerance groups; namely, high, moderate and low. Cluster analysis of the SLTAS scores indicated that Iranian EFL learners were mostly moderate as far as tolerance of ambiguity was concerned. Examining the gender differences through an independent sample t-test manifested that female participants were less tolerant of ambiguity than their male peers. Also, the differences between the expected and observed number of participants categorized in the three AT groups were non-significant undermining the role of gender as a moderator variable in assigning participants to AT groups and further approving of SLTAS validity. Implications for classroom practice are presented in the light of findings. The results are helpful in syllabus design and teaching methodology.