Cadmium (Cd) is a highly toxic element for living organisms. Its toxicity and the thereof by calcium (Ca) in 2-week-old Arabidopsis seedlings were studied. The seedlings were treated with Cd at concentrations of 50–500 µM for 24 h. Retardation of root growth was evident through increased cell death at the root elongation zone. Supplementing with 30 mM Ca restored root elongation in the presence of up to 200 µM Cd, resulting in up to a 1/3 decrease in Cd content in the seedlings compared to Arabidopsis treated with Cd alone. Ca was able to alleviate Cd toxicity, presumably through competition for metal ion influx. These results provide us with information regarding plant ion uptake systems and metal ion toxicities.