Background: This study aimed to assesses critical thinking skills among psychiatric mental health nursing students. Study design was a descriptive research design. The study was conducted on 90 psychiatric mental health students at Faculty of nursing, affiliated to Ain Shams University. The type of sample was convenient sample. Data were collected using The California Critical Thinking Dispositions Inventory questionnaire (CCTDI) it divided into two parts (1) socio-demographic characteristics sheet (2) critical thinking assessment sheet. The results: this study revealed that the majority of sub-scales of CCTDI students showed a negative disposition toward critical thinking. No statistical significant difference was found in relation of critical thinking disposition and age and residence. The study concluded that, the majority of psychiatric mental health's nursing students have the highest mean percentage about skills of critical thinking in “truth seeking followed by open mindedness and inquisitiveness meanwhile, the lowest mean percentage of dispositional level characteristics of “self-confidence" among psychiatric mental health students. The most of psychiatric mental health nursing students have negative disposition toward clinical thinking. The study recommended that, Nursing educational program for enhancing critical thinking skills and how to apply, the students must play an active role in designing this program. Short courses workshops are recommended to develop critical thinking skills. Revising the curriculum and preparing nurse educators for implementation of innovative and active teaching strategies are suggested.