The basic psychological needs for autonomy, competence, and relatedness in self-determination theory (SDT) were originally defined and interpreted as necessary for well-being. Although this necessity assumption has been a cornerstone of SDT for over three decades, no systematic evidence has yet emerged to support it. This knowledge gap largely stems from a theory-method misfit. Most empirical studies use regression-based analytical techniques that do not align with necessity logic because they reflect a probabilistic “average-effect” logic. Necessary condition analysis (NCA) is an appropriate method specifically designed for identifying necessary conditions. In the present research, we adopt NCA to examine whether autonomy, competence, and relatedness are necessary for employee evaluative well-being (job satisfaction and work meaningfulness), affective well-being (positive affect), and conative well-being (work engagement). Across three studies, we found consistent support for the necessary role of psychological need satisfaction in all four well-being indicators, with nuanced variations in these necessity relationships. In contrast, power and status were not found to be necessary. These findings advance our understanding of basic psychological needs through a necessity-oriented lens and underscore the importance of fostering a need-supportive work environment in organizations.