The daily biological rhythms of many organisms are regulated by a near 24-hour circadian clock. In plants, the central oscillator controls a range of important physiological output processes such as flowering, stress and hormone responses, and regulation of nutrient acquisition. In this work, we investigated the effect of Fe deficiency on the circadian clock and found that it lengthened the circadian period. The functional status of chloroplasts under Fe deficiency may play a key role in the lengthened circadian period. Fe availability is still an agricultural problem worldwide. Revealing the interplay between Fe homeostasis and modulation of the circadian clock can help increase understanding of their contributions to plant growth and development.