UV-cured plastic scintillators capable of miscibility with aqueous solutions were developed and characterized. We selected a water-miscible monomer, M-240. The photoinitiator concentration and UV irradiation time were optimized to obtain samples having high scintillation light yields. All fabricated scintillators had an emission peak at approximately 450 nm and an excitation peak at 350–400 nm in the photoluminescence emission and excitation spectra, respectively. The scintillation spectra also had a peak at around 450 nm, which is attributed to the emission of 1,4-Bis(5-phenyl-2-oxazolyl)benzene included in the scintillators as wavelength-shifting molecules. Using the optimized conditions, we evaluated the effect of adding distilled water on the appearance of the scintillators and their scintillation light yields at different concentrations of the fluorescent molecules. The addition of distilled water up to approximately 8 wt% resulted in a decrease in the scintillation light yield by less than 40%. On the basis of these results, we have successfully developed UV-cured plastic scintillators containing aqueous solutions.