Cryptococcosis is a severe fungal infection, particularly in immunosuppressed individuals, causing over 112,000 HIV-related deaths annually. Early and accurate diagnosis is critical, but current methods often lack the necessary sensitivity, specificity, and accessibility for point-of-care use. A major challenge is identifying highly specific bioreceptors for detecting Cryptococcus-specific antibodies. This study addresses these diagnostic limitations by developing a novel biosensing approach. While biosensor technology holds significant promise for rapid, sensitive, and selective responses in healthcare, effective solutions for cryptococcosis, particularly antibody detection, remain challenging. The surface plasmon resonance (SPR) technique was employed as the transduction system for constructing the biosensor. A new synthetic multiepitope protein, called protein D, was evaluated as a bioreceptor for developing an SPR immunosensor. Protein D is a chimeric protein composed of five different peptides (H18, H21, H26, S4, and Hy49) linked in specific combinations. The proposed SPR immunosensor presented limits of detection (LOD) of 0.1 μg mL^–1 and quantification (LOQ) of 0.5 μg mL^–1. Analysis of human sera was performed with high selectivity and reproducibility, effectively discriminating between individuals with and without cryptococcosis. To date, no plasmonic immunosensing system has been reported for detecting fungal Cryptococcus antibodies in human serum. In brief, this study successfully demonstrated the viability of a synthetic multiepitope protein in an SPR immunosensor for the serological diagnosis of cryptococcosis.