Leaf water potential (ψl) represents a good indicator of the water status of plants, and continuous monitoring of it can be useful in research and field applications such as scheduling irrigation. Changes in stem diameter (Sd) were used for monitoring ψl of pot‐grown sorghum [Sorghum bicolor (L.) Moench] plants in a glasshouse. This method requires occasional calibration of Sd values against ψl. Predicted values of ψl based on a single calibration show a good correlation with measured ψl values over a period of 13 d before and after the calibration. The correlation can further be improved with shorter time intervals.