Ornamental plants growing in urban areas are often exposed to salt stress that negatively affects their decorative value. Enhancement of their salt resistance to retain a high decorative value despite salt stress has therefore high practical importance. In our study, the exposure of Plectranthus scutellarioides (L.) R. Br. to NaCl-induced moderate (40 mM) or severe salt stress (80 mM) resulted in a number of stress responses including reduced growth parameters, decreased concentration of photosynthetic pigments, and an increase in the accumulation of anthocyanins and free proline. These changes were partially compensated for by the application of selenium (5 μM as Na2SeO4) to the growth medium. However, the beneficial effect of selenium on the growth and physiological parameters of P. scutellarioides was manifested only at the moderate level of salt stress. Under the severe salt stress, the application of selenium was not able to alleviate the phytotoxic effect of NaCl.