This article describes the development, implementation, and evaluation of an online professional development course designed to develop an understanding of the foundations, perspectives, and strategies used by key disciplines (e.g., occupational therapy, physical therapy, speech-language pathology, early childhood special education, visual impairment, and hearing loss) that provide services for infants with multiple disabilities and for their families. A total of 110 early interventionists in California completed the online course successfully. An overview of the course content, structure, assignments, and online instruction is provided. A discussion of outcomes includes feedback from participants on (1) their perception of changes in their own professional competencies based on pre- and post-test data, (2) their satisfaction with the overall course design, (3) challenges and benefits of online instruction, and (4) the impact of what they learned on their professional practice. Implications for future professional development efforts are identified. (Contains 4 tables.)