Natural radionuclides such as 40K, 226Ra and 228Ra are found naturally in water and sediments of rivers, likewise in soils. They are transferred to aquatic animals through ingestion. Radioactivity concentrations and dose rates of 40K, 226Ra and 228Ra in crayfish species from Ode Omi River in coastal region, Ogun State Southwest of Nigeria were determined by gamma spectrometry using NaI (TI) detector coupled with a pre-amplifier base to a multiple channel analyzer (MCA). 15 samples of crayfish were collected. Cherax tenuimanus had the highest mean concentration and dose rate of values 106.87 ± 9.11 Bq kg–1 and 0.00960 mGy hr–1 respectively for 40K. Moreso, for 226Ra, Cherax quadricarinatus had the highest mean concentration and dose rate of values 2.57 ± 0.82 Bq kg–1 and 4.50 x 10–7 mGy hr–1 respectively. Concerning228Ra, Astacopsis gouldi had the highest mean concentration and dose rate of values 5.23 ± 0.46 Bq kg–1 and 5.86 x 10–13 mGy hr–1, respectively. The average dose rate of the radionuclides in all the crayfish was calculated to be 4.62 x 10 ̶ 3 mGy hr–1 which was below the 0.4 mGy hr–1 limit recommended. The average annual committed effective dose and average excess lifetime cancer risk of all the radionuclides to the consumers were 0.0807 mSv yr–1 and 0.589 x 10–4, respectively, which were below global limits of 1.0 mSv yr–1 and 0.29 x 10–3, respectively, therefore, the ingestion of these natural radionuclides could not pose any radiological health hazards to the aquatic animals, likewise man the consumers. Keywords: Radionuclide concentration, Dose rate, Cancer Risk.