Spatial distribution of radon in groundwater in the coastal tracts of southern Kerala, India was studied to understand its linkage with the monazite bearing beach sand deposits in the area. The mean radon concentrations were below the guideline value recommended by United States Environmental Protection Agency in about 94 % samples analyzed. Annual effective ingestion and inhalation doses of water-borne radon were found to be well below the average doses reported from all natural sources. The study indicated that radionuclides in the monazite-rich beach sands do not contribute significantly to the radon concentration in groundwater in the area.