Analysis of program fidelity, defined by adherence to intervention design, exposure, quality of delivery, and participant responsiveness, was examined in an IYCF program in Ethiopia. Results suggest evidence of strong fidelity in training and delivery of tools and messages at higher levels, but gaps in reach to community volunteers and mothers as well as variance between regions limit potential impact. These findings point to a need to strengthen the linkages between health extension workers and volunteers to deliver results at scale.