AIMS AND OBJECTIVES: To explore caregiver’s strain, the relationship between social support and caregiver’s strain and the predictors of caregiver’s strain among mothers with school-aged intellectually disabled children in Taiwan. BACKGROUND: Strain is a common condition among mothers who take care of intellectually disabled children; this correspondingly reduces their ability to care for children, thereby affecting the functioning of the entire family. Yet, there have been very few studies on caregivers of intellectually disabled children of school age. DESIGN: Cross-section correlational design. METHODS: Data collection consisted of face-to-face interviews combined with a structured questionnaire. Instruments employed were the Caregiver Strain Index, Social Support Scale and three open-ended questions. In total, 127 mothers completed the questionnaire. RESULTS: Results showed that mothers with intellectually disabled children had a rather high level of strain and received inadequate social support. Social support and strain had a significant and negative correlation. Stepwise regression analysis revealed that mothers’ health status, social support and amount of time spent as a caregiver, as well as the intellectually disabled children’s dependent degree of daily living activity, were major predictors of caregiver’s strain, which accounted for 38.4% of the total variance. CONCLUSIONS: The results provide a guide for healthcare professionals in designing effective interventions and preventive care to reduce the level of strain in mothers with intellectually disabled children. This, in turn, could improve the quality of life of the mother and her family. RELEVANCE TO CLINICAL PRACTICE: In Taiwan, care of intellectually disabled children is primarily provided by family members. Therefore, we should emphasise family-centred care to enable healthcare professionals to become more effective as case managers in local clinics, schools and communities.