The idea that parents' ability to collaborate and support each other (co-parenting) has a protective effect within the family system has received increasing attention in recent years. Indeed, literature has highlighted how parents' ability to be good allies - ensuring a solid, cohesive and supportive family environment - promotes good parent-child interactions and children's psychological well-being. On the contrary, it has been highlighted that conflictual co-parenting and its weakening could favor dysfunctional interactions and emotional and behavioral problems in children. This volume, thanks to the fruitful collaboration of several expert international researchers, describes the main instruments (questionnaires and diaries) and observation procedures used to ensure a correct assessment of coparenting, with appendices providing detailed descriptions of the multi-method instruments and procedures, their fields of application and guidelines for administration and coding. It therefore represents a useful resource for both professional psychologists and researchers interested in promoting well-functioning family dynamics.