The structure and electrostatics of liquids change dramatically under nanometric confinement, suggesting that solvent-solute interactions in such environments differ fundamentally from those in the bulk. Here, we combine nanoscale Fourier-transform infrared spectroscopy (nanoFTIR) with the vibrational Stark effect (VSE) to directly map the local electric field experienced by a molecular probe—the C=O stretching vibration of dimethylformamide (DMF)—within buried nanofluidic channels. To this end, we fabricated hexagonal boron nitride (hBN)-capped trenches with depths ranging from ~100 nm down to 2.6 nm and filled them with a 1:1 (v/v) aqueous DMF solution.