Avascular necrosis (AVN) of the femoral head is a progressive disorder that predominantly affects young, active adults and frequently culminates in femoral head collapse and secondary osteoarthritis if left untreated. Core decompression combined with biological augmentation has been explored as a joint-preserving alternative to arthroplasty in early-stage disease. Autologous cultured osteoblasts, expanded ex vivo from the patient's own bone marrow or periosteal tissue, offer a theoretically attractive strategy to enhance osteogenesis at the necrotic focus while avoiding the immunogenicity and disease-transmission risks of allogeneic tissue. Objective: To evaluate the clinical and radiological outcomes of core decompression combined with implantation of autologous cultured osteoblasts in patients with ARCO Stage I and II avascular necrosis of the femoral head, over a minimum follow-up of six years. Materials and Methods: Fifteen hips in 13 patients (12 men, 3 women; mean age 33.8 years) with ARCO Stage I (n = 6) or Stage II (n = 9) AVN of the femoral head underwent core decompression followed by injection of culture-expanded autologous osteoblasts derived from iliac crest bone marrow aspirate. Patients were evaluated using the Harris Hip Score (HHS) and Visual Analogue Scale (VAS) for pain preoperatively and at 6 months, 1, 2, 3, 4, 5 and 6 years. Radiological staging (ARCO) and progression to collapse or conversion to total hip arthroplasty (THA) were recorded. Results: Mean HHS improved from 56.5 ± 6.2 preoperatively to 86.8 ± 8.5 at final follow-up (p < 0.001), and mean VAS score decreased from 6.5 ± 0.9 to 1.8 ± 1.3 (p < 0.001). Twelve of 15 hips (80%) showed no radiological progression at final follow-up. Three hips (20%) progressed radiologically to Stage III, of which one (6.7%) ultimately required conversion to total hip arthroplasty at 48 months. No major procedure-related complications occurred. Conclusion: Core decompression augmented with autologous cultured osteoblasts is a safe, reproducible, and effective joint-preserving option in ARCO Stage I and II AVN of the femoral head, providing durable pain relief and functional improvement and delaying or averting the need for arthroplasty in a majority of patients at 6-year follow-up. Larger, controlled, multicentric studies are warranted to confirm these findings.