Purpose: Current research and theory in spelling development and best practices for literacy instruction were reviewed to develop a set of theoretically guided assessment and intervention procedures. These procedures were applied to the case of a 13-year-old student with spelling difficulties. Method: The student was involved in an intensive group intervention program that focused on increasing foundational skills for spelling and on oral word-level reading. Assessment results led to an intervention program targeting phonemic and morphological awareness skills and orthographic knowledge. Results: The student demonstrated clinically significant growth in phonemic and morphological awareness, orthographic knowledge, spelling, and word-level reading. Conclusion: Results of the case study suggest that assessment and intervention procedures guided by theory and research can lead speech-language pathologists to effective participation in aspects of spelling remediation. Additionally, the case study may serve as a model for clinical services and evidence-based practice within clinical settings.