There is a worldwide need for tools to assist young children who learn English as a second language (ESL). The authors have been implementing two approaches to designing robot/child interaction activities for ESL children : one-on-one learning in play and small-group learning in play. In the former approach, a child interacted with an embodied robot individually to develop vocabulary and early literacy skills. Based on our study of theories of learning and child development, we sought to create engaging robot-based learning, where the child played with the robot to practice the skills. Through our experience, it was clear that pedagogically solid design and iterative refinement led to sustainable robot/child interaction. The latter approach is currently being explored in our on-going research. Acknowledging that language learning and cultural understanding are inseparable, we examine the role of a robot as a cultural broker that mediates collaborative learning and play among children from different cultural and linguistic backgrounds. During the workshop, we will discuss our motivation toward this approach and pedagogical grounding for the approach, and the progress that has been made in the design of robot-mediated