Previous studies have found that a stressful observational context challenges the mother-child relationship, thus highlighting negative interactive behavior. However, the impact of observational context has only been investigated in infants and preschoolers without specifically using the Emotional Availability Scales. Nor have they explored whether the association of mother-child interaction with children’s emotional or behavioral problems depends on the observational context. We observed 140 mothers and their five to 12-year-old children in non-stressful free play and in a stressful task context. In general, dyads showed higher emotional availability in the task context compared to the free play. Specifically, mothers showed higher levels of Sensitivity, Structuring and Nonhostility, but lower levels of Nonintrusiveness during the task compared to the free play context; children showed higher levels of Responsiveness during the task than during free play. After controlling for dyadic stress, contextual effects decreased for all dimensions of emotional availability. The association of mother-child interaction with child problem behavior depended on the observational context. Specifically, we found maternal emotional availability during free play to be more strongly associated with child problem behavior than during the stressful task; however, emotional availability of the child was more strongly associated with problem behavior when obtained during the task. We conclude that context impacts on mother-child interactive behavior and also on the association of mother-child-interaction and child behavior. Stress is a relevant contextual factor influencing mother-child interactive behavior.