Background: Mental retardation is a life-long disability and has a major impact on the lives of the children and mothers. Caring child with mental retardation affects several aspects of mother's life negatively including poor physical and emotional state. Aim: Evaluate the effect of instruction module on mothers' knowledge and coping patterns regarding care of children with mental retardation. Research design: This study utilized a quasi-experimental (pre/posttest) design. Settings: Psychiatric Outpatient Clinics in Children's Hospital affiliated to Ain Shams University. And outpatient clinics for children at the Psychiatric Mental Health Hospital in Benha City, Qalubia Governorate. Tools of data collection: Tool (1): A structured interviewing questionnaire (pre/post): It was divided into two main parts: Part (1): Characteristics of the study subjects, and Part (2): Mothers' knowledge regarding mental retardation Tool (2): Selfreliance Assessment. Tool (3): Coping patterns scale. Results: There was a highly statistical significant difference (P value <0.001) between pre, immediate post application of the instruction module in relation to mothers' total knowledge, self-reliance assessment, and coping patterns regarding care of children with mental retardation. Conclusion: There were highly statistical positive correlation between total level of the mothers' knowledge, selfreliance assessment and coping strategies at post instruction module phase. Recommendations: provide ongoing educational initiatives aimed at enhancing the understanding of mothers with children experiencing mental retardation, ensuring they acquire sufficient knowledge and practical skills, and enhancing patterns of coping strategies