Un-irradiated potassium citrate exhibited a weak ESR singlet at g = 2.0045 +/- 0.0003 with peak-to-peak line-width of Delta H-pp = 0.16 mT. However, multi-resonance signals spreading over a magnetic field range of similar to 5 mT were observed in gamma irradiated potassium citrate. A linear function of absorbed radiation dose was found to describe well the dose-response curves of the resonance signals A, B and C in a dose range of 5-5000 Gy. Room temperature fading study showed that radiation-induced radicals in potassium citrate are highly stable but less stable when exposed to the sunlight. Three different radical species were found to describe well experimental room temperature ESR spectrum of irradiated potassium citrate. The resonance signal B can be used in measuring the accidental radiation doses and the radiation doses used in food industry, at least up to a dose of 5 kGy. Further studies were needed in order to increase the sensitivity of potassium citrate at low radiation doses.