Of the many widely known stressors for couples, in-laws rank among the top five problematic areas (Schramm, Marshall, Harris & Lee, 2005). Interference is a major complaint for couples with regard to in-laws, and the mother-in-law has been identified as the most detrimental to marital satisfaction. The present study sought to determine the effect of perceived boundaries on the relationship between interference and marital satisfaction using a newly developed measure and the Revised Dyadic Adjustment Scale from the perspective of married females. 241 married females completed an online survey about their perceptions of their mothers-in-laws behavior and their husbands boundary-setting behavior. The results demonstrated that the effect of interference on marital satisfaction is mediated by the perceived boundaries that are set by participants husbands for their mothers. These findings highlight the importance of couples communication about in-law difficulties and further ground family systems theory and Bowens triangle theory. In addition, the new instrument may have useful clinical applications.