Arsenic (As) and cadmium (Cd) in soil are solubilized and immobilized under contrasting redox conditions. Tradeoff relationships have been recognized between dissolved As and Cd in soil, and between As and Cd in rice grains. Recent studies, however, have suggested the possibility of simultaneous suppression of As and Cd concentrations in rice grains by appropriate water management strategies. A key notion underlying the strategies is that dissolved As is rapidly immobilized once the air-filled porosity of soil exceeds a threshold value upon drainage, whereas solubilization of Cd is a slower process which continues after the completion of As immobilization. This leads to a hypothesis that by conducting intermittent irrigations with an appropriate drained period, dissolved As and Cd concentrations are simultaneously kept at low levels, resulting in suppression of their uptake by rice plants. The objective of this study was to find an optimal intermittent irrigation interval for reducing rice grain As while minimizing the increase in rice grain Cd. The study was comprised of Field Experiments I and II, both of which examined the effects of intermittent irrigation during preheading 3 weeks and postheading 3 weeks on dissolved as well as rice grain As and Cd concentrations. In Field Experiment I conducted in four fields, intermittent irrigations with different irrigation intervals (4–10 days) were compared. Intermittent irrigations with a drained period of 3 days or longer substantially lowered dissolved As concentration in soil during postharvest 3 weeks, which was critical to rice grain As. Intermittent irrigation repeating 3-day flooding and 4-day drainage was capable of achieving acceptably low levels of rice grain As and Cd concentrations simultaneously. In Field Experiment II, feasibility of this intermittent irrigation strategy with 3-day flooding and 4-day drainage was further tested at 21 sites for two years. On average, rice grain inorganic As concentration was lowered by 38% relative to the continuous flooding at sites where the latter exceeded 0.2 mg kg−1. Adverse effects on rice grain Cd, grain yield and quality were minimized in most cases. Further field experiments are in progress to develop a more versatile water management strategy to reduce rice grain As and Cd concentrations.