Plants respond to Cd by synthesising phytochelatins (PC) and similar S‐rich peptides which are important in alleviating Cd toxicity. The hypothesis that S nutrition influences the sensitivity of plants to Cd was examined by measuring the growth, PC and Cd content of wheat plants (Triticum aestivum cv. Condor) grown at 10–1000 µM S with and without 30 µM Cd. In the absence of Cd, 100 µM S was marginally S‐limiting. Cd severely inhibited root growth at 100 µM S but the concentrations of PC, Cd–PC complexes and Cd in the root were similar to those of plants grown at 1000 µM S which exhibited no evidence of Cd toxicity. Plants grown at low S (10 and 30 µM) contained lower concentrations of Cd. However, they produced very low amounts of PC and were very sensitive to Cd. At 10–300 µM S (but not at 1000 µM), Cd enhanced the concentration of S in the root. The data are consistent with a model in which plants preferentially allocate S to PC synthesis. When S was marginally limiting (100 µM), the S supply was sufficient for PC synthesis but not root growth, effectively causing Cd‐induced S deficiency. This did not occur at high S (1000 µM). Conversely, at low S (10 and 30 µM), the synthesis of PC2–PC4 was decreased by 87 and 66%, respectively, thereby resulting in decreased Cd uptake while also making the plants especially sensitive to Cd.