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Recent experiments on twisted bilayer WSe₂ have shown signatures of interlayer moiré excitons in a wide range of twist angles. The emission spectra of the excitonic states manifest strong valley polarization which is absent in naturally occurring 2H stacked homobilayer counterparts. However, the underlying mechanism of the excitonic states and their exotic polarization properties is still elusive. In this work, we investigate the interlayer moiré excitonic states in the twisted bilayer WSe₂ using first-principles GW-BSE calculations. We first perform density functional theory (DFT) calculations and study how moiré potential and interlayer hybridization affect the spin-valley properties of the system. To investigate the quasiparticle and optical properties, we next perform GW and GW-BSE calculations with the recently developed pristine unit-cell matrix projection (PUMP) [1] method and explore the role of spin and valley degrees of freedom in the polarization properties of interlayer moiré excitons.