Excess Phosphorus (P) in agriculture is causing serious environmental problems like eutrophication of lakes and rivers. Unlike the enormous information available for phosphate starvation response (P0), very few information is available for the effect of excess phosphate Pi on plants. Characterization of Excess Phosphate Response (EPiR) is essential for designing strategies to increase phosphate accumulation and tolerance. We show a significant modulation in the root developmental plasticity under the increasing supply of excess Pi. An excess supply of 20 mM Pi (P20) produces a shallow root system architecture (RSA), reduces primary root growth, root apical meristem size, and meristematic activity in Arabidopsis. The inhibition of primary root growth and development is indeterminate in nature and caused by the decrease in number of meristematic cortical cells due to EPiR. Significant changes occurred in metal nutrients level due to excess Pi supply. A comparative microarray investigation of the EPiR response reveals a modulation in ethylene biosynthesis and signaling, metal ions deficiency response, and root development related genes. We used ethylene-insensitive or sensitive mutants to provide more evidence for ethylene-mediated signaling. A new role of EPiR in regulating the developmental responses of plants mediated by ethylene has been demonstrated.