An absorber covering the visible to infrared spectrum can be utilized in various sensor applications. In this study, we designed and fabricated a multilayer absorber with the following structure from bottom to top: an iron substrate, followed by alternating layers of silicon dioxide (SiO2) dielectric and metal layers in the order of iron (Fe), SiO2, chromium (Cr), SiO2, titanium (Ti), SiO2, Ti again, and a top antireflective layer of magnesium fluoride (MgF2). Through simulation and optimization, the absorber achieved an average absorptivity of 97.8% across a broad wavelength range from 350 to 2600 nm. Analysis revealed that this ultrabroadband and high absorption performance results from a combination of factors, namely, the antireflective effect of the MgF2 layer on the top surface and the interplay of three distinct resonance mechanisms, which are Fabry–Perot resonance, propagating surface plasmon resonance, and localized surface plasmon resonance. These mechanisms work synergistically to enhance absorption across the target spectrum. Subsequently, the optimized absorber was deposited onto a silicon substrate by electron beam evaporation. The surface morphology and cross-sectional structure were examined by scanning electron microscopy, whereas the absorber’s performance across the ultraviolet (UV), visible (Vis), and near-infrared (NIR) ranges was evaluated using a UV/Vis/NIR spectrophotometer.