Nowadays, the development of simple, fast, and low-cost selective sensors to detect substances of interest is of great importance in several application fields. Among this kind of sensors, those based on surface plasmon resonance (SPR) represent a promising category, since they are highly sensitive, versatile, and label-free. In this work, an SPR probe, based on a poly(methyl methacrylate) (PMMA) slab waveguide covered by a gold nanofilm, combined with a specific molecularly imprinted polymer (MIP) receptor for bovine serum albumin (BSA) protein, has been realized and experimentally characterized. The obtained experimental results have shown a limit of detection (LOD) equal to about 8.5 × 10−9 M. This value is smaller than the one achieved by another SPR probe, based on a D-shaped plastic optical fiber (POF), functionalized with the same MIP receptor; more specifically, the obtained LOD was reduced by about three orders of magnitude with respect to the POF configuration. Moreover, concerning the D-shaped POF configuration, no manufacturing process is present in the proposed sensor configuration. In addition, fibers are used only to connect the simple sensor chip with a light source and a detector, promoting a bio-chemical sensing approach based on disposable, low-cost, and removable chips.