Fathers’ support is crucial to relieve mothers’ strain as caregivers for persons with intellectual disability (PIDs), but its amount and effectiveness are unknown in Chinese families given the traditional parenting roles. This study aimed to investigate the amount of fathers’ support and how it could influence mothers’ caregiving strain and marital satisfaction from mothers’ perspective. With a cross sectional design, this survey recruited mothers of persons with intellectual disability in Hong Kong through convenient sampling. A total of 154 mothers were recruited. 61.1% of participating mothers reported to receive less than 1 h of support from fathers in their caring work per day. The commonest type of support provided by fathers was help in managing PIDs’ misbehaviors (47.7%), followed by providing training to PIDs (45.4%). Higher marital satisfaction was associated with more than 1 h of support per day and higher parenting alliance, as well as the presence of support in training, playing, and managing misbehaviors. In contrast, higher caregiving strain was to a greater extent related to the characteristics of persons with intellectual disability, namely the presence of autism diagnosis, inadequate self‐care abilities, and with challenging behaviors. Surprisingly, caregiving strain was not related to the amount of support mothers received. Fathers’ assistance in self‐care and escort were both associated with lower caregiving strain, but the former was the least reported by mothers (22.5%). General linear model analyses suggested that higher parenting alliance was significantly associated with marital satisfaction after controlling other measured variables; while inadequate self‐care abilities and presence of challenging behaviors remained as significant predictors to higher caregiving strain. From mothers’ perspective, fathers’ support in their caring work was crucial. The findings provide important implications on how to maximize the effectiveness of support to promote higher marital satisfaction and lower caregiving strain among mothers.