To ensure quality patient care hospitals invest in nursing intellectual capital by allocating financial, human and material resources for nurses to acquire the knowledge and skills necessary to provide safe patient care. This study’s purpose was to test selected propositions of the middle-range theory of nursing intellectual capital which provides a conceptualization of the influence of nurses’ knowledge, skills and experience (nursing human capital) to patient and organizational outcomes. The theory was systematically developed after a critical review of the literature. It proposes that nursing human capital (registered nurses’ experience, and knowledge and skills acquired from continuing professional development including university courses, conferences, workshops, in-services, specialty certification) is related to variables within the work environment (nurse staffing, employer support for nurse continuing professional development), which in turn, is associated with the quality of patient care (adverse events) and the recruitment and retention of nurses. The theory also proposes that nursing structural capital, nursing knowledge available within practice guidelines, is associated with the quality of patient care. A cross-sectional design was used to test the proposed relationships.