The long term success of periodontal treatment is dependent upon the effectiveness of the maintenance care program after active treatment. The purpose of this study was to evaluate whether nutraceutical containing PRF-K2 as natural product from plant and seaweed has beneficial effects on clinical parameters, gingival crevicular fluid (GCF) volume and GCF cytokine levels during maintenance phase after periodontal treatment. Among the generally healthy and non-smoking, moderate to severe chronic periodontitis patients during maintenance phase in Department of Periodontics, Chonnam National University Hospital, twenty eight patients took nutraceutical containing PRF-K2 (Oscotec Inc. Cheonan, Korea) for 3 months as experimental group and sixteen patients received only maintenance care as control group. Clinical examination and GCF collection were performed at baseline, 1, 2 and 3 months of experiment. Total amounts and concentrations of GCF IL-1beta, IL-1ra and PGE2 were evaluated using ELISA kit. In probing pocket depth, experimental group showed the tendency of more reduction than control group after 3 months of experiment. Sulcus bleeding index (SBI) and GCF volume were significantly decreased in experimental group(p<0.05), whereas they were increased in control group. GCF IL-1betalevel tended to decrease in both experimental and control group and IL-1ra concentration tended to increase in experimental group and to decrease in control group. IL-1ra/IL-1beta ratio tended to increase in experimental group and to decrease in control group during experimental period. GCF PGE2 amount did not show any change in experimental group and tended to increase in control group. These results suggest that nutraceutical supplement which contain PRF-K2 could improve periodontal condition during maintenance phase after periodontal therapy.