Quality is a multidimensional issue involving various features that depend on service performance and personal assessment. Clarifying the concept of quality is essential in order to further facilitate the understanding and improvement of quality in healthcare. The purpose of this study was to investigate how clinical nurses, providing care to adult medical patients, perceive and define the concept of quality nursing care. A descriptive qualitative research design was applied. A purposive sampling strategy was used to recruit nurses from the clinical sector of a general public hospital in Athens, Greece. Ten female nurses from the medical sector participated the study. Data collection was conducted through in-depth, semi-structured interviews. Conventional content analysis was used to analyze the verbatim data. Four categories were revealed from the data analysis, namely: (a) “Quality care is holistic care”, (b) “Good care is an interpersonal issue”, (c) “Leadership is crucial”, and (d) “Best care is our responsibility”. Quality care was defined as holistic care, addressing all patient needs with competency and aiming for the best patient outcomes. It was associated with communication, teamwork, good leadership, and personal commitment. By developing an in-depth and mutual understanding about what quality means, nurse leaders and practitioners may collaborate in finding common paths to support quality interventions and enhance quality nursing care in clinical practice.