Background: Natural background radia on of a par cular region is one of the dis nc ve factors defining the status of environment. Eloor Island is an industrial area in Ernakulum District of the state of Kerala, India. The indoor and outdoor gamma level measurements have been carried out for the region for evalua ng the annual effec ve dose to the popula on residing in this area. Materials and Methods: Measurements of indoor gamma dose were done for a whole year using Thermo Luminescent Dosimeters (TLDs) and GM tube based survey meters in forty five selected loca ons. The ac vity concentra on of 232 Th, 238 U and 40 K in the samples were analyzed using gamma spectrometry. The outdoor external gamma ray dose rates were evaluated from the ac vity concentra on of 40 K. From the observed mean dose levels, the annual effec ve dose equivalent to popula on residing in the island has been es mated and is found to be 0.68 mSv y -1 for indoors and 0.32 mSv y -1 for outdoors. Conclusion: The annual effec ve dose equivalent to popula on es mated for indoor is found to be higher as compared to the global average the same for outdoor was found to be less when compared with the natural background gamma level reported by UNSCEAR for normal background areas.