Illegal use of melamine, a nitrogen-rich compound, in food products such as milk poses serious health threats, including renal toxicity and infant mortality, even at concentrations just above regulatory limits. This urgent public health concern demands the development of rapid, sensitive, and cost-effective analytical methods for reliable detection of melamine in complex food matrices. In this investigation, silver nanoparticles immobilized on electrospun hexagonal boron nitride nanofibers (Ag/h-BN NFs) have been engineered as a functional substrate for constructing a high-performance SERS-based sensor, enabling sensitive detection of melamine in milk. The high surface area-to-volume ratio of h-BN nanofibers promotes the uniform deposition of silver nanoparticles, thereby generating abundant plasmonic hot spots and offering efficient charge-transfer pathways that contribute to chemical enhancement. The induced plasmonic hotspots around the Ag nanoparticles in the proximity of h-BN fibers were evaluated using theoretical simulations based on the finite-difference time-domain (FDTD) method. The developed Ag/h-BN NF-based SERS sensor was used to detect melamine at trace-level concentrations within the permitted range from 5 μM to 250 μM, demonstrating the possibility of the developed substrate to detect melamine at trace-level concentrations down to 5 μM. Furthermore, the practical applicability of the proposed method in food analysis was validated through the detection of melamine in liquid raw milk, achieving a detection limit as low as 0.5 mg/L (4 μM) using the Ag/h-BN NF-based SERS substrate. This work thus presents a promising strategy for the rapid and sensitive identification of melamine adulteration in milk samples.