The effect of antioxidant stimulators on low phenolic and high phenolic single seed originating creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.] clonal lines were investigated to understand whether these natural compounds could improve the physiological adjustments of creeping bentgrass under low temperature exposure. A marine peptide hydrolysate, and chitosan oligosaccharide (COS) derived from marine chitin were applied to creeping bentgrass foliage and then subjected to cold temperature (4°C, day/night temperature) for 3 wk. Significant stimulation of total phenolic content (8%-CB 27 to 75%-CB 15) and antioxidant enzyme response (16%-CB 27 to 44% CB 13) was observed in creeping bentgrass clonal lines following application of marine peptide + COS. Superoxide dismutase (SOD) (13–50%), and guaiacol peroxidase (GPX) activity (58–99%) increased significantly after treatments in all creeping bentgrass clonal lines, and stimulation of antioxidant enzyme activity was more profound in low phenolic creeping bentgrass clonal lines. Higher glucose-6-phosphate dehydrogenase (G6PDH) and higher proline dehydrogenase (PDH) activity was also observed in these lines following application of marine peptide + COS. Stimulation of pentose phosphate pathway (PPP) and a probable proline oxidation in creeping bentgrass clonal lines after foliar application of marine peptide ± COS suggest a role for the enzymes in the improvement of these lines.