This study attempted to examine the extent to which university instructors contributed as obstacles or facilitators to developing critical thinking skills in undergraduate, graduate, and doctorate students. To this end, six university classes, two classes from each of the above-mentioned programs, were selected randomly from the Department of Foreign Languages and Linguistics in a State University. The corpus of the study was collected via video recordings during a semester. Vygotsky’s (1978) sociocultural theory was utilized to interpret the data. The results revealed that instructors in BA and one of MA classes were facilitators of critical thinking skills, while those in the other MA class and both Ph.D. classes acted more as obstacles to such skills. This finding contradicted the expectations of the researcher who, based on Fisher’s (2005) arguments, believed that thinking skills should be more developed at tertiary levels by instructors, particularly as one moves from bachelor to master and doctoral levels, which are more about frontiers of knowledge. The implications of the study pointed to the vital role of the university instructors in promoting thinking skills by decreasing interruptions, increasing wait-time, asking referential questions, and using selective repair.