Serum creatine kinase (CK) is routinely used as a marker in the assessment of rhabdomyolysis and acute myoglobinuric kidney injury (Mb-AKI), while the use of myoglobin is much less explored in this respect. We retrospectively analyzed the incidence of Mb-AKI (creatinine [Cr] > 200 μmol/L) and the need for hemodialysis (HD) in 484 patients (70.5% males) with suspected rhabdomyolysis, grouped according to peak serum myoglobin (A: 1-5 mg/L, B: 5-15 mg/L, C: >15 mg/L). The median peak myoglobin was 7163 μg/L. Both peak Cr and peak CK were significantly higher in group C. The incidence of Mb-AKI was 24.6% in group A, 38.6% in group B (P < 0.01 vs. group A), and significantly higher (64.9%) in group C (P < 0.001 vs. groups A and B). Fifty-one patients (10.5%) needed HD, the proportion increasing from 6.7% in group A, and 12.3% in group B (NS), to 28.1% in group C (P < 0.001 vs. group A, P 0.01 vs. group B), and reaching 36.8% with myoglobin >20 mg/L. Creatine kinase correlated with the severity of rhabdomyolysis, but less so with Mb-AKI. The peak Cr levels were not significantly different between patients divided by CK 60 μkat/L, or grouped into CK tertiles or quartiles. A significant proportion of patients with rhabdomyolysis experienced Mb-AKI, whose frequency increased in parallel with myoglobin levels. Myoglobin levels above 15 mg/L were most significantly related to the development of AKI and the need for HD. Blood myoglobin could serve as a valuable early predictor and marker of rhabdomyolysis and Mb-AKI.