Increased intracellular iron levels can both promote cell proliferation and death, as such; iron has a "two-sided effect" in the delicate balance of human health. Though the role of iron in the development of cancer remains unclear, investigations of iron chelators as anti-tumor agents have revealed promising results. Here, we investigated the influence of iron and desferrioxamine (DFO), the iron chelating agent on intracellular calcium in a human leukemia cell line, K562. Iron uptake is associated with increased reactive oxygen species (ROS) generation. Therefore, we showed that iron also caused dose-dependent ROS generation in K562 cells. The measurement of intracellular calcium was determined using Furo-2 with a fluorescence spectrophotometer. The iron delivery process to the cytoplasmic iron pool was examined by monitoring the fluorescence of cells loaded with calcein-acetoxymethyl. Our data showed that iron increased intracellular calcium, and this response was 8 times higher when cells were incubated with DFO. K562 cells with DFO caused a 3.5 times increase of intracellular calcium in the presence of doxorubicin (DOX). In conclusion, DFO induces intracellular calcium and increases their sensitivity to DOX, a chemotherapeutic agent.