Abstract: Reclaimed minesoils have well-defined ages (time since reclamation), making them suitable for studying temporal changes in terrestrial carbon sequestration. The objective of this research was to assess the effect of time since reclamation on soil organic carbon (SOC) sequestration and related soil properties such as texture, bulk density, and cation exchange capacity in three West Virginia minesoils along a chronosequence. The minesoils’ surface 750 Mg ha−1 (0–6 cm) was sampled at 1, 4, and 21 years and again at 2, 5, and 22 years postreclamation, giving a total of 6 site-years of information. Average SOC stocks (Mg C ha−1) were highest in the oldest minesoils. Soil bulk density was highest and unrelated to SOC concentration in the youngest minesoil, reflecting recent compressive reclamation techniques. The cation exchange capacity of older minesoils was influenced more by SOC than by clay, whereas the opposite was observed in younger minesoils. The relationship of SOC stock to time since reclamation was best described by a logarithmic diminishing returns model. Short-term (1 year) SOC sequestration rates (Mg C ha−1 y−1) were not appropriate to describing the change in SOC sequestration rate occurring along the chronosequence. When taken as the first derivative of the diminishing returns model, long-term SOC sequestration rates were shown to decline precipitously (80%) in the first 5 years after reclamation. The model predicts that the surface 750 Mg ha−1 of minesoil will contain about 13.3 Mg SOC ha−1 at 50 years after reclamation. About 75% of that SOC storage is predicted to be achieved in the first decade after reclamation.