A newly developed red Chinese cabbage (Brassica rapassp. campestris; CC) was analyzed to determine the changes in functional compounds, especially in phenolic compounds. In the red CC, cyanidin was the major anthocyanidin, with 4.11 mg·g−1dry weight (dw), while pelargonidin and peonidin were minor components. The control CC, however, contained no anthocyanidins. In both CCs, four hydroxycinnamic acids were detected, and sinapic acid was the principal compound found. Hydroxycinnamic acids in the red CC were significantly more abundant than were those in the control, by a factor of 1.4–13.3. Quercetin was the principal flavonol in the red CC, with 2.7 mg·g−1dw, whereas it was the flavonol with the lowest concentration in the control CC (0.5 mg·g−1dw). Kaempferol and isorhamnetin concentrations were also increased in the red CC by 1.41- and 3.10-times, respectively. The results imply that, due to the common synthetic pathways of the phenolic compounds, the creation of a red phenotype from the presence of anthocyanidin increased the levels of flavonols and phenolic acids. Pectin, reducing sugar, and cellulose levels in the red CC indicate that the red CC could be preferred by consumers because of its better taste. Consequently, the new red CC, by accumulating significant amounts of the bioactive anthocyanidin, has significant value for human nutrition.