Background Positive Deviance/Hearth (PDH) is an internationally recognized nutrition rehabilitation program. However, nutritional improvements are inconsistent across contexts. It is unclear if variations are from differences in program design, implementation, utilization, or other contextual factors. Furthermore, few PDH programs have addressed the high time- and work-burden of caregivers and volunteers. To address this, the study integrated interactive voice calls (IVC) with PDH. Objectives A program impact pathway (PIP) analysis was used to evaluate the secondary outcomes of facilitators, barriers, and contextual factors that influence PDH-IVC design, implementation, and utilization to improve the nutritional status of children in Cambodia. Methods The study was registered at clinicaltrials.gov[NCT03399058]. A PIP analysis was done on data collected through in-depth interviews with caregivers (n = 32), key informant interviews with volunteers (n = 16) and project staff (n = 3), and surveys of project staff (n = 5). Results In design phase, facilitators included quality training, technical support and design tools, community mobilization, and linkage to existing health services. Barriers included poor community mobilization. For the implementation phase, facilitators were good volunteer knowledge, follow-up tools and guidance, supervision, and spot checks of volunteers. Barriers were lack of time and overworked, older caregivers. For the utilization phase, facilitators included family and volunteer support and access to phones while barriers were lack of support, time, and financial resources, low levels of education and old age of caregivers, and inconsistent phone use. Contextual factors included food insecurity and increased childcare responsibilities on grandmothers due to migration of mothers. Conclusions The PIP analysis identified facilitators, barriers, and contextual factors that may affect the design, intervention, and utilization and elements to consider when designing and implementing IVC interventions for health and nutrition behavior change. When implementing child nutrition programs in Cambodia, supporting interventions addressing mental health and time and resource constraints of elderly caregivers should also be included.