AbstractReactivation of denatured rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1) was found to be aided by the presence of serum albumin. Both the rate and the extent of reactivation of the urea‐denatured enzyme were optimal at low rhodanese and moderate serum albumin concentrations. Similarly, stabilization of the sulfurtransferase activity of rhodanese that had been partially unfolded at 40°C was aided by the presence of serum albumin. All the observations are in accord with a model in which enzyme that has been partially refolded from the urea‐denatured state or partially unfolded thermally interacts directly with serum albumin in a way that prevents rhodanese self‐association. Serum albumin thus acts as a molecular chaperone in these s