Mitochondria produce adenosine triphosphate (ATP), the main source of cellular energy. To maintain normal function, cells rely on a complex mitochondrial quality control (MQC) system that regulates mitochondrial homeostasis, including mitochondrial dynamics, mitochondrial dynamic localization, mitochondrial biogenesis, clearance of damaged mitochondria, oxygen radical scavenging, and mitochondrial protein quality control. The MQC system also involves coordination of other organelles, such as the endoplasmic reticulum, lysosomes, and peroxisomes. In this review, we discuss various ways by which the MQC system maintains mitochondrial homeostasis, highlight the relationships between these pathways, and characterize the life cycle of individual mitochondria under the MQC system.