Recent years have witnessed widespread adoption of α-phase molybdenum trioxide (α-MoO₃) in biosensing owing to its in-plane anisotropic characteristics. We propose a bifunctional surface plasmon resonance biosensor employing the Kretschmann configuration that operates in the visible to near-infrared wavelength range and demonstrates a bifunctional capability defined by two core features: (1) In the wavelength-interrogation mode, the in-plane anisotropy of α-MoO₃ allows active performance tuning—x-polarization achieves high sensitivity (Sx = 8250 nm RIU−1), while y-polarization achieves a high figure of merit (FOMy = 570.89/RIU). (2) The same sensor configuration also supports robust resonance angle-shift detection, confirming its versatility as a multi-mode platform.