Growing evidence suggests current water, sanitation, and hygiene interventions do not improve domestic hygiene sufficiently to improve infant health, nor consider the age-specific behaviors which increase infection risk. A household playspace (HPS) is described as one critical intervention to reduce direct fecal-oral transmission within formative growth periods. This article details both the design and development (materials and methods), and testing (results) of a HPS for rural Ethiopian households. Design and testing followed a multi-sectoral, multistep participatory process. This included a focus group discussion (FGD), two user-centered and participatory design workshops in the United Kingdom and Ethiopia, discussions with local manufacturers, and a Trials by Improved Practices (TIPs) leading to a final prototype design. Testing included the FGD and TIPs study and a subsequent randomized controlled feasibility trial in Ethiopian households. This multi-sectoral, multistage development process demonstrated a HPS is an acceptable and feasible intervention in these low-income, rural subsistence Ethiopian households. A HPS may help reduce fecal-oral transmission and infection-particularly in settings where free-range domestic livestock present an increased risk. With the need to better tailor interventions to improve infant health, this article also provides a framework for future groups developing similar material inputs and highlights the value of participatory design in this field.