Aim: This study aimed to clarify the value of caring programs developed according to Orem's Self-Care Deficit Nursing Theory regarding quality of life and self-care as the primary outcomes and self-efficacy, anxiety, depression, and stress as the secondary outcomes among individuals aged 18-70 years with chronic diseases.

Background: Chronically ill patients need to receive appropriate self-care training, counseling, and support. In this regard, the use of caring programs developed based on theories is highly suggested. Orem's Nursing Theory is the most well-known theory that provides a structure to involve patients in their self-care activities.

Introduction: Orem's Nursing Theory has been increasingly applied to guide practice for patients with chronic health conditions. However, recent trials have reported conflicting findings on the value of its application.

Methods: Eight information sources (e.g., Web of Science Core Collection, PubMed, and Scopus) and the International Clinical Trials Registry Platform were searched up to 30 March 2022.

Results: A total of 46 studies and 11 study register entries were eligible. Orem's theory-based interventions significantly improved the quality of life, self-care, and self-efficacy as well as significantly reduced anxiety and depression. However, the value of the interventions on stress was uncertain, as performing the meta-analysis was not possible.

Discussion: Orem's Nursing Theory can help nurses in different fields to dynamically and carefully evaluate patients' self-care ability and implement appropriate nursing measures tailored to their needs, interests, and problems. Considering the inconsistent evidence to support the empirical adequacy of this theory, high-quality reviews are essential.

Conclusion: Orem's theory-based programs had a favorable effect on taking care of adults with chronic diseases.

Implications: This study augments the previous reviews related to the applicability of Orem's Nursing Theory. Considering the undesirable evidence quality and the high between-study heterogeneity, further well-designed trials are required to draw an evidence-based conclusion.