This research is part of the summative evaluation of Ready To Learn, a partnership between the US Department of Education, the Corporation for Public Broadcasting, and PBS, that seeks to develop engaging, high-quality educational programming and supports for two- to eight-year-old children growing up in low-income households. A core aim of the initiative is delivering early mathematics and literacy transmedia resources on new and emerging digital platforms such as tablet computers, interactive whiteboards, and smartphones, as well as better-established technologies such as computers, video displays, and gaming consoles, and to create learning experiences that leverage the unique capabilities of these various technology platforms for young children's learning. For the purpose of this study, transmedia means the use of familiar characters, settings, and narrative themes or stories across different media formats, such as digital video, interactive online games, and interactive whiteboard applications. This study demonstrated that preschool children who participated in a media-rich curriculum incorporating PBS KIDS transmedia improved significantly in their understanding of key early mathematics skills essential for school success. In addition, teachers who implemented the media-rich curriculum reported significant increases in their confidence and comfort with early mathematics concepts and beliefs about the benefits of teaching with technology. (author abstract)