<p>Calcium (Ca²⁺) is an essential macronutrient for plant growth and defence, yet the molecular mechanisms regulating its uptake from soil remain largely undefined. Through bioinformatics and electrophysiological screening, we identified a group of plant-specific proteins, named the IONIC CURRENT FAMILY A (ICAs), which confer Ca²⁺-permeable non-selective cation channel (CNCC) activities in heterologous systems. In <i>Arabidopsis thaliana</i>, <i>AtICA1</i>, <i>AtICA2</i>, <i>AtICA3</i> and <i>AtICA4</i> are predominantly expressed in root cells, and their proteins localize to the plasma membrane. Under either limited or excessive external Ca²⁺ conditions, <i>ica1/2/3/4</i> quadruple mutants display hypersensitivity or reduced sensitivity, respectively, as evidenced by altered root length. In addition, these mutants show increased sensitivity to various abiotic and biotic stresses under normal Ca²⁺ conditions. The <i>ica</i> mutants lack the previously characterized CNCC-mediated currents in roots that facilitate cellular Ca²⁺ uptake, resulting in lower Ca²⁺ levels compared with wild-type (WT) plants. Our findings suggest that AtICA1/2/3/4 may function as components of CNCCs, mediating Ca²⁺ uptake crucial for broad environmental stress tolerance under normal Ca²⁺ conditions. This study provides molecular insight into the mechanisms governing Ca²⁺ uptake in plant roots and expands our understanding of how plants maintain Ca²⁺ homeostasis under varying environmental conditions.</p>