The activity concentration of naturally occurring radionuclides ⁴⁰K, ²²⁶Ra and ²³²Th have been measured in different brands of fertilizer samples in Saudi Arabia using sodium iodide gamma spectrometry. The results of measurements showed that the mean (ranges) of specific activities for ²²⁶Ra, ²³²Th and ⁴⁰K activities in the nitrogen, phosphorus and potassium fertilizers are 64 (35.8 - 120.7), 17 (3.2 - 56.8) and 2453 (744.9 - 4227.1) Bq/kg, respectively. With respect to organic fertilizers under investigation, the average radioactivity of ²²⁶Ra, ²³²Th and ⁴⁰K are 42, 10 and 333 BqKg^?1, respectively. Radium equivalent activity is not exceed 370 Bq/kg, the maximum permissible limit for radiation dose for all present samples. Average values of the three natural radionuclides measured in the brands of fertilizers used in Saudi Arabia are within the range of values reported in several other countries. This study could be useful as baseline data for radiation exposure to fertilizers and their impact on human health.