The C + ion photofragment spectra and photodissociation branching ratios into the two energetically available channels, C( 1 D) + O( 3 P) and C( 3 P) + O( 3 P), have been obtained for the three CO isotopologues, 12 C 16 O, 13 C 16 O, and 12 C 18 O, in the vacuum ultraviolet range 100500−102320 cm −1 . The two vibronic states of 1 Σ + symmetry, F(3dσ) 1 Σ + (υ′ = 1) and J(4sσ) 1 Σ + (υ′ = 0), predominantly dissociate into the lowest channel C( 3 P) + O( 3 P) through interactions with the repulsive D′ 1 Σ + state. All three vibronic states of 1Π symmetry, E′ 1 Π(υ′ = 1, 2) and G(3dπ) 1 Π(υ′ = 0), dissociate into both of the channels above. The photodissociation branching ratios into the channel C( 1 D) + O( 3 P) for E′ 1 Π(υ′ = 1, 2) are found to be independent of both the rotational quantum number and e/f parity, while those for G(3dπ) 1 Π(υ′ = 0) strongly depend on the rotational quantum number, indicating very different predissociation pathways between the valence states E′ 1 Π(υ′ = 1, 2) and the Rydberg state G(3dπ) 1 Π(υ′ = 0). The potential energy curves of CO in the aforementioned energy range and below have recently been well constructed due to a series of interplays between high-resolution spectroscopic studies and theoretical calculations; the photodissociation branching ratios measured in this study can provide further benchmarks for future theoretical investigations which aim to understand the detailed predissociation dynamics of CO.