Biological and chemical threats pose significant security risks to all societies. While biological threats can cause health crises through the spread of pathogenic agents, chemical threats can have detrimental effects on the environment and human health through the spread of toxic substances. They can target critical infrastructure and lead to emergency management, health crises, or economic disruptions in societies. The deployment of protective equipment and sensor systems is extremely important in establishing an effective protection and detection system against these threats. While protective equipment provides a physical barrier, sensor systems provide rapid and accurate detection of threats. Electrospun nanofibers are an important material used in protective equipment and sensor systems in combating chemical and biological threats. Due to their high surface area and thin structure, these nanofibers provide effective filtration. In addition, their lightness and comfort facilitate long-term use, while their water resistance and durability extend the life of protective equipment. In sensor systems, nanofibers provide high sensitivity and fast response time, helping to rapidly and accurately detect chemical and biological agents. Surface modifications also allow the development of sensors and protective equipment specific to specific threats. This book chapter presents current approaches and future directions of electrospun nanofibers for protection, decontamination, and detection against various chemical and biological threats, based on a synthesis of recent studies.