This study investigated the influence of auxins on the growth of hairy roots and accumulation of anthocyanins, including cyanidin 3-O-glucoside (C3gl) and cyanidin 3-0-rutinoside (C3r), in the hairy root culture of tartary buckwheat cultivar Hokkai TIO. C3gl and C3r contents were evaluated using high- performance liquid chromatograph (HPLC). Four auxins, 2,4-dichlorophenoxyacetic acid (2,4-D), indoleacetic acid (IAA), indolebutyric acid (IBA) and naphthaleneacetic acid (NAA), were added to the medium of the hairy root cultures at diverse concentrations. IAA, IBA and 2,4-D promoted the growth of hairy roots since the dry weight of the roots was slightly higher than or comparable with that of the control. However, NAA at all concentrations suppressed the growth of hairy roots. Generally, auxin treatments resulted in higher accumulation of C3gl and C3r than that of the control except for 2.85 μM IAA and 2.69 μM NAA. The amount of C3gl and C3r after treatment with 4.92 μM IBA was the highest among all treatments and was 3.24 times more than that of the control. Our results suggested that auxins at appropriate concentrations might facilitate hairy root growth of tartary buckwheat and enhance the production of C3gl and C3r.