Background: Nursing theories are organized bodies of knowledge providing a way to define nursing as a unique discipline that is separate from other disciplines. As a profession, nursing is committed to recognizing its own unparalleled body of knowledge vital to nursing practice and science. Nursing is a science based on the theory of what nursing is, what nurses do, and why. Aim: This paper aims to elucidate the practical application of Hildegard Peplau's and Rosemarie Parse's nursing theories, individually and in synthesis, in modern nursing practice. Key points: These include a) Hildegard Peplau's Theory of Interpersonal Relations emphasizes the nurse-patient relationship, therapeutic communication, and the continuous search for improvement in patients, even those facing mental health challenges. b) Rosemarie Parse's Theory of Human Becoming underscores the uniqueness of each patient's lived experiences, the significance of "meaning" in health experiences, "rhythmicity" in patterns, and the potential for "transcendence" and growth. c) Integrating Peplau's and Parse's theories promotes holistic patient-centered care, compassionate and empathetic nursing, enhanced communication skills, patient autonomy, cultural competence, continuity of care, and a deep respect for human dignity. d) By embracing both theories, nurses can provide comprehensive, compassionate, and patient-centered care that respects each patient's individuality and capacity for growth. Conclusion: The synthesis of Hildegard Peplau's and Rosemarie Parse's nursing theories offers nurses a comprehensive framework for modern nursing practice. It guides nurses in providing high-quality, patient-centered care that preserves human dignity and recognizes the uniqueness of each patient. Drawing from multiple theoretical perspectives enhances nursing practice and ensures the well-being of patients in today's evolving healthcare landscape.