INTRODUCTION: Transitioning from academic education to clinical practice is challenging for newly graduated nurses. This study evaluated a 12-month culturally tailored internship on professional competence, self-efficacy, and perceived health among newly graduated Saudi nurses. METHODS: A longitudinal design with repeated measures was used to recruit 147 female Saudi newly graduated nurses who completed an internship program at two tertiary hospitals. Data were collected at beginning, 8 months, and completion of the program. The Nurse Professional Competence Scale-Short Form, General Self-Efficacy Scale, and self-reported health measures were used. Statistical analyses were conducted using analysis of variance (ANOVA) with post hoc comparisons. RESULTS: Significant improvements were found in professional competence, especially in leadership, documentation, and administrative skills. Value-based care competence remained high. Self-efficacy and perceived health were also improved. DISCUSSION: Culturally tailored internship programs are effective in enhancing newly graduated nurses' professional competence and perceived health. Such internship programs may effectively help to enhance training for practice-ready nurses.