Purpose: This study examined the quality characteristics and antioxidant activities of konjac jelly to which premature mandarin peel powder had been added. Methods: The quantities of premature mandarin peel powder added to the konjac jelly were 0 g, 1.5 g, 3 g, 4.5 g, and 6 g. The quality characteristics, sensory evaluation scores, and antioxidant activity of the konjac jelly were measured. Results: The konjac jelly pH decreased (p<0.001) when the levels of premature mandarin peel powder added increased. The sugar content of all the samples of konjac jelly was similar except for the 0 g konjac jelly sample (p<0.05). Color measurements showed that L value and b value increased, but a value decreased as the levels of premature mandarin peel powder added increased (p<0.001). The moisture content tended to decrease (p<0.001) with the addition of the premature mandarin peel powder. On the other hand texture, hardness, chewiness and gumminess showed a tendency to increase (p<0.001). However, springiness (p<0.05) and cohesiveness (p<0.001) decreased with the addition of premature mandarin peel powder. The sensory evaluation showed that konjac jelly containing 3 g of premature mandarin peel powder had the highest rating in all sensory tests. Intensity ratios showed color, premature mandarin peel flavor, bitterness, and intensity increased as the levels of premature mandarin powder were increased (p<0.001). Antioxidant activity results revealed that the konjac jelly containing 6 g premature mandarin peel powder had the highest rating in total polyphenol and flavonoid content (55.22 mg GAE/100 g, 99.26 mg RE/100 g (p<0.001)). Also, DPPH and, ABTS free radical scavenging tended to increase when the premature mandarin peel powder was added. Conclusion: The addition of premature mandarin peel powder improves the quality characteristics and antioxidant activities of konjac jelly and this powder could be used with various other products, too.