Parasitic diseases impose a profound global health and economic burden, particularly in resource-limited settings where rapid and accurate diagnostic infrastructure is lacking. Traditional diagnostic methods often fall short in sensitivity, specificity, and point-of-care adaptability. Aptamers—single-stranded DNA or RNA oligonucleotides selected in vitro via systematic evolution of ligands by exponential enrichment (SELEX)—have emerged as highly stable, cost-effective, and versatile biorecognition elements capable of binding diverse targets with high affinity and specificity. This review explored the mechanisms of aptamer-based biosensors (aptasensors) and their emerging applications in diagnosing strategic parasitic infections, including malaria, leishmaniasis, Chagas disease, Human African Trypanosomiasis, and giardiasis. Despite challenges, such as nuclease degradation and SELEX-related biases, aptamer-based biosensors demonstrate significant potential as reliable, sensitive, and specific tools for next-generation diagnosis and monitoring of parasitic diseases.