In the title compound, C(23)H(24)N(4)O(3)·H(2)O, the 1,3-oxazoline ring is nearly planar [maximum deviation = 0.059 (2) Å] and its mean plane is twisted by 30.12 (8)° with respect to the quinoxaline fused-ring system; the benzene ring is nearly coplanar with the quinoxaline fused-ring system [dihedral angle = 2.52 (2)°]. The water mol-ecule of crystallization is hydrogen-bond donor to an N atom...