This study assessed effects of intrinsic factors, composition and candy size, and extrinsic factors, storage temperature, and humidity, on moisture sorption characteristics of hard candy. Nine types of plain hard candy with various percentage of sucrose (45.0 to 65.0% wt/wt) and citric acid (0.0 to 1.0% wt/wt) were prepared. The prepared samples had surface area per weight ratio (SA/W) of 2.05 to 3.69 cm2/g. Moisture sorption isotherms of all candy formulations were built at 25 °C and 35 °C and were well‐represented by Guggenheim‐Anderson‐de Boer (GAB) model (R2 between 0.9634 and 0.9960). Compositions and SA/W significantly affected moisture sorption characteristics of hard candies. Increasing citric acid content increased rate of moisture uptake, while increasing SA/W decreased absorption rate. Additionally, the predictive models for rate of moisture uptake of candies with different compositions and SA/W at 25 °C and 35 °C and 75% relative humidity based on second‐order response surface methodology were developed and validated. Practical applications Moisture sorption isotherms built and the obtained models of moisture uptake could be used as a guideline to predict moisture sorption characteristics or to estimate shelf life of hard candies, with known compositions and/or storage conditions.