Antarctic toothfish (Dissostichus mawsoni) are subject to an increasingly important commercial fishery in the Southern Ocean, yet many of their life history characteristics, including vital rates, remain unknown. In this study, Antarctic toothfish were aged using otolith age estimation criteria established for Patagonian toothfish, D. eleginoides, a closely related species. To validate estimated ages, the radioactive disequilibrium of lead-210 and radium-226 in otolith cores was measured and used as an independent chronometer to determine age. Age estimates indicated Antarctic toothfish live to at least 39 years of age. Estimated and radiometric ages were in close agreement, confirming age estimation criteria and an annual periodicity of otolith growth zones. Von Bertalanffy growth function parameters indicate Antarctic toothfish are relatively slow-growing (k = 0.111; t0 = -0.605), especially in relation to their maximum size (L∞ = 158.9 cm). These vital rates are discussed in the context of the growing Antarctic toothfish fishery.