In this study, novel growth of WO3-ZnSe nanocomposites was carried out by a simple, low-cost hydrothermal process under subcritical conditions and is reported for the first time in just 5 h. The products were characterized in detail by multiform techniques: X-ray diffraction, scanning electron microscopy (SEM), optical studies, and Fourier transform analysis. The influence of ZnSe on the structural, morphological, compositional, optical, and catalytic properties of WO3 is demonstrated. The WO3 metal oxide material is grown in a hexagonal crystal structure with wide-band-gap and has been modified by ZnSe to form a composite nanostructures in the nanoscale range. The electrochemical properties of the prepared materials were studied by cyclic voltammetry, which revealed that the synthesized material exhibited remarkable electrochemical supercapacitive activity. Moreover, the composite nanostructures showed excellent photocatalytic activity for degradation of phenol and almost 93% of phenol was degraded with good recyclability and stability. According to The International Commission on Illumination (CIE), the synthesized nanomaterial shows blue emission and is suitable for blue LEDs. [ABSTRACT FROM AUTHOR]