In spring 2015, WestEd conducted a study for the CPB-PBS Ready To Learn Initiative of a school- and home-based transmedia mathematics intervention based on the resources in the PBS KIDS Odd Squad transmedia suite. The transmedia mathematics intervention, called Odd Squad Math, or OSM, for purposes of the study, included a wide variety of Odd Squad transmedia assets, including episodes from the television series, educational online games, interstitials (i.e., short video clips), and hands-on activities. The current study addresses how children use and learn in transmedia learning environments. A primary feature of the intervention is a transmedia learning environment that includes high-quality video episodes, digital games, and hands-on activities for classroom and home. All learning materials are connected by a strong narrative and carefully curated mathematics content. During the intervention, students are invited to enter the world created by the narrative and to work with its appealing characters to solve mathematics problems in a fun, engaging learning environment. The purpose of the study was to test the promise of using Odd Squad Math to enhance first-grade students' mathematics learning. (author abstract)