Bioaerosols, in addition to common gaseous or particulate pollutants, are also important air pollutants that deteriorate indoor air quality. Bioaerosols are the airborne particles present as or originating from living organisms such as fungi, bacteria, and viruses and include toxins, fragments, or waste product from various organisms. In this chapter, the characteristics of indoor bioaerosols are provided. The common type and sources of bioaerosols are summarized. These biological pollutants are commonly generated both by the activities and behaviors of the occupants, and by housing materials and substances that penetrate from the outdoor environment. Fungi and bacteria are the most common bioaerosols present in the indoor environment. After exposure, occupants may experience adverse health outcomes such as infection or allergy. If the indoor environment is severely contaminated, as observed in many places during the COVID-19 pandemic, especially in public areas, a large number of people may be affected by contamination. This chapter also summarizes monitoring and assessment technologies. The monitoring procedure can be chosen and performed according to the objective of the assessment. Advance technologies such as real-time sensor monitoring, Internet of Things, and artificial intelligence have been integrated, but their use for bioaerosols monitoring is still limited as compared to their use for other types of indoor air pollutants. Effective control strategies to reduce the contamination of indoor bioaerosols are also provided in this chapter that could benefit occupants to reduce the contamination and minimize exposure.