There is a lack of research on effective interventions to improve the early numeracy skills of children with severe disabilities---autism spectrum disorder, developmental disability, and intellectual disability---and complex communication needs. While preliminary research suggests the Early Numeracy curriculum is effective for teaching children with severe disabilities, efficacy of this curriculum has not yet been examined for students with co-occurring complex communication needs. Using a multiple probe across participants research design, we evaluated the efficacy of the Early Numeracy curriculum for increasing targeted math skills of four children with severe disabilities and complex communication needs. Results indicated a functional relation between the intervention and improvements in early math skills. Limitations and future research needs are discussed.