Introduction: Although humor plays an important role in improving people s mental and physical health, empirical studies on the effectiveness of humor skills training to improve the symptoms of the patients with schizophrenia are scarce. Objective: This study aimed to determine the effectiveness of humor skills training on positive and negative symptoms in male patients with chronic schizophrenia spectrum. Materials and Methods: This research has a quasi-experimental design with pretest-posttest and control group. The statistical population consisted of male patients with chronic schizophrenia admitted to rehabilitation centers in Ardabil City, Iran. A sample of 30 patients were selected with cluster random sampling method and randomly divided into two groups of experimental (n=15) and control (n=15). Members of both groups were pretested and humor skills training program using the McGee 8-step plan was administered to the experimental group for 8 sessions. To collect the data, the Positive and Negative Syndrome Scale (PANSS) was used. The obtained data were analyzed using Analysis of Covariance (ANCOVA). Results: Positive and negative symptoms scores significantly decreased after 8 sessions of humor skills training in the experimental group (P=0.001) while there was no significant difference between pretest and posttest scores in the control group (P>0.05). Conclusion: Humor skills training decreased positive and negative symptoms in patients with schizophrenia. Therefore, using this program is recommended to reduce the problems of patients with schizophrenia.