This study investigated differences in total phenolic content (TPC), antioxidant capacity, and phenolic acids in free, conjugated and bound fractions of white (unpolished), red and black rice at 1-, 2-, and 3-weeks of grain development after flowering and at maturity. Unlike the TPC (mg/100 g) of white rice (14.6–33.4) and red rice (66.8–422.2) which was significantly higher at 1-week than at later stages, the TPC of black rice (56.5–82.0) was highest at maturity. The antioxidant capacity measured by DPPH radical scavenging and ORAC methods generally followed a similar trend as TPC. Only black rice had detectable anthocyanins (26.5–174.7 mg/100 g). Cyanidin-3-glucoside (C3G) and peonidin-3-glucoside (P3G) were the main anthocyanins in black rice showing significantly higher levels at 2- and 3-weeks than at 1-week development and at maturity. At all stages, the phenolic acids existed mainly in the bound form as detected by HPLC and confirmed by LC–MS/MS. Black rice (20.1–31.7 mg/100 g) had higher total bound phenolic acids than white rice and red rice (7.0–11.8 mg/100 g). Protocatechuic acid was detected in red rice and black rice with relatively high levels at 1-week development (1.41 mg/100 g) and at maturity (4.48 mg/100 g), respectively. Vanillic acid (2.4–5.4 mg/100 g) was detected only in black rice where it peaked at maturity. p-Coumaric acid (