"Symbiosis," meaning "with" and "living," describes an ecological relationship between two organisms from different species that is sometimes, but not always, beneficial to both parties. One such relationship is mutualism, which is a mutually beneficial symbiotic relationship. In a mutualistic symbiotic relationship, when one of the two organisms is not present, the other suffers. Such is the case with social and emotional learning (SEL) and mathematics learning. SEL is the process through which all young people and adults acquire and apply the knowledge, skills, and attitudes to develop healthy identities and meet personal and collective goals. Competencies for SEL are defined by the Collaborative for Academic, Social, and Emotional Learning. Likewise, competencies for mathematics are defined by the Standards for Mathematical Practice or other process standards that describe what doing mathematics looks like. This article briefly explores how to attend to these two learning "organisms" and then offers tasks at each grade band as examples of what it looks like to attend to both competencies and have the benefit from the mutualism between the two.