Theory of mind (ToM) allows people to understand their own and others' behaviour, crediting it with intentions, desires and beliefs. In the case of parenting, maternal reflective function unfolds within child-caregiver interactions, and previous studies have pointed out this variable as necessary for positive care. In the present study we sought to understand how high levels of stress could interfere with their reflective function capacity, and how this relates to children's ToM. A sample of 125 mothers and their preschool children (36-54 months) was assessed. It was hypothesized that the maternal reflective function would play a mediating role between the parental stress variable and the preschooler's ToM. The study found that parental stress exerted direct and significant effects on the mother's reflective function and direct but mild effects on the child's ToM. In addition, different elements of parental stress would act differently on the mother's reflective function.