Background: Chronic kidney disease (CKD) disrupts mineral metabolism and is associated with increased levels of ‘Fibroblast Growth Factor-23’ (FGF-23), a main ‘regulator of phosphate homeostasis’. FGF-23 levels have been linked to inflammation, ‘serum phosphate’ dysregulation, and ‘bone mineral density’ (BMD) abnormalities. Understanding these relationships is essential for improving outcomes in ‘CKD patients’. The objective was to assess the association of FGF-23 with C-reactive protein (CRP), serum phosphate, and BMD in patients with CKD. Methodology A cross-sectional study was conducted on CKD patients at Bacha Khan Medical College Mardan, examining FGF-23, CRP, serum phosphate, and BMD. Inclusion criteria were patients aged 18–65 years with stage 3–5 CKD. Exclusion criteria included patients with acute infections, recent fractures, or malignancies. Serum levels of FGF-23, phosphate, and CRP were measured, while BMD was assessed using dual-energy X-ray absorptiometry (DEXA). Data were analyzed using SPSS software. Results The study involved 200 participants. FGF-23 ‘levels were significantly correlated with CRP’ (p less than 0.01) and serum phosphate (p less than 0.01). Patients with higher FGF-23 levels had lower BMD (p < 0.05). ‘Multivariate regression analysis’ showed that FGF-23 ‘was an independent predictor’ of inflammation and bone mineral abnormalities in CKD patients. Conclusion FGF-23 is strongly associated with inflammation, phosphate dysregulation, and reduced bone mineral density in CKD patients. Addressing FGF-23 levels may offer therapeutic potential in mitigating the complications associated with CKD.