Quantum well infrared photodetectors (QWIPs) are widely utilized in long-wave infrared detection applications, yet they are constrained by low quantum efficiency. Although metallic microcavities can enhance local coupling, achieving a field strength that perfectly coincides with the quantum well layers remains challenging, and such approaches are often incompatible with thick active regions. In this study, we developed an all-dielectric metasurface-coupled QWIP (MS-QWIP) to enhance device response. The metasurface features a square micropillar array etched directly into the 80-period GaAs/AlGaAs multi-quantum wells active region. By leveraging the guided-mode resonance effect, this structure excites a strong longitudinal electric field component, effectively satisfying the intersubband transition selection rule for enhanced absorption within the active region. Experimental results at 50 K and a 5 V bias show that the peak responsivity of the MS-QWIP reaches 545 mA/W, a twofold increase over a conventional 45° facet-coupled device. Furthermore, the blackbody responsivity is improved by approximately 1.6 times. Notably, the architecture also reduces the effective electrical area of the photosensitive element, thereby suppressing dark current. This work demonstrates that all-dielectric metasurfaces can significantly enhance the sensitivity and signal-to-noise ratio of QWIPs.