The increasing number of chronically ill people has served as an impetus for the promotion of patient participation in nursing care. However, little is known about patient participation in Iran. The aim of this study was to identify the factors that are relevant to patient participation and the nature of that participation, as experienced by chronically ill patients and registered nurses in Iran. Grounded theory was used as the method. Twenty-two participants were recruited by using purposeful and theoretical sampling. The data were generated by semistructured interviews and participant observations. Constant comparison was used for the data analysis. This study indicated that participation is an interactive process between nurses, patients, and family members in the caregiving context. Participation occurred when the caring agents worked together. The core category of “convergence of the caring agents” emerged. The subcategories emerged as the levels of participation and included “adhering”, “involving”, “sharing”, and “true participation”. The factors related to the caring agents and caregiving context could be considered as predictors of the level of participation when caring for these patients.