Patients suffering from beta thalassemia major experienced iron overload due to hemolysis, increased iron absorption in the gastrointestinal tract, and primarily due to repeated blood transfusions. This iron accumulation was exacerbated by the lack of a physiological mechanism for the body to naturally eliminate excess iron. One of the main complications of this condition was iron toxicity, which could damage various organs, including causing renal dysfunction. The persistence of this condition was associated with an increased risk of kidney injury, which could potentially lead to acute kidney injury and renal complications. The objective of the present study was to ascertain the correlation between serum ferritin levels and eGFR in adult patients diagnosed with beta thalassemia major in order to achieve the third focus of Sustainable Development Goals (SGD’s) in good health and well-being. The present study was a quantitative research study that utilized an observational analytic design with a cross-sectional approach. It was based on secondary data from the medical records of adult patients with beta thalassemia major at the Department of Internal Medicine, Universitas Airlangga Hospital. Subjects were selected using consecutive sampling. The statistical analysis of the correlation between serum ferritin levels and eGFR was conducted using Spearman tests. A total of 62 adult patients with beta thalassemia major were include this study, with mean age of 26 years. The majority of participants (42 patients or 67,7%) had serum ferritin levels below 1000 ?g/L. All of Subjects (62 patients) had eGFR within the normal range, all were classified as G1 (> 90 mL/min/1.73 m²). The Spearman analysis results showed a weak positive correlation between serum ferritin levels and eGFR with a correlation coefficient (r = 0.277) and a p-value of 0.029. Conclusion: There is a weak positive correlation between serum ferritin levels and eGFR in adult patients with beta thalassemia major.