There were few studies reported the temporal trend of radioactivity in water and food. Here, using Hangzhou (Zhejiang, China) as a case study, we determined the radioactivity (⁹⁰Sr, ¹³⁷Cs, gross alpha, and gross beta) levels and temporal variations in water and food samples during 2012–2019, and in the meanwhile the ¹³⁷Cs/⁹⁰Sr activity ratios were calculated and a dose assessment was performed. Results showed that the ⁹⁰Sr and ¹³⁷Cs concentrations in water varied from (1.6–17.2) × 10⁻³ and (0.66–15.1) × 10⁻³ Bq/L, respectively. The temporal variations in gross alpha and gross beta radioactivity of water were small, except those for Qiantang River. Radioactivity levels of gross alpha (< 0.016–0.059 Bq/L) and gross beta (< 0.028–0.69 Bq/L) in water were lower than World Health Organization recommendations. In food samples, ⁹⁰Sr concentrations varied from 0.029–1.3 Bq/kg fresh weight while ¹³⁷Cs concentrations were mostly below the minimum detectable activity except for haritail (up to 0.13 Bq/kg); both were significantly below the limits recommended by Chinese national standard for radiation safety. ⁹⁰Sr and ¹³⁷Cs concentrations were relatively constant in water samples across the entire study period. Significant variations were observed in the ⁹⁰Sr concentrations of foods among different years and different food types. The available activity ratios of ¹³⁷Cs/⁹⁰Sr in food and water samples demonstrate notable increase in the period of 2015–2017, which further enlightens the potential existence of local radioactive release in the study region, though without causing any radiation safety concerns. This study indicated that all annual effective doses estimated for water and food ingestion were below the permissible limits and recommendations.