Mitochondria are energy factories of cells and are important for intracellular interactions with other organelles. Emerging evidence indicates that mitochondria play essential roles in the response to pathogen infection. During infection, pathogens deliver numerous enzymes and effectors into host cells, and some of these effectors target mitochondria, altering mitochondrial morphology, metabolism, and functions. To defend against pathogen attack, mitochondria are actively involved in changing intracellular metabolism, hormone-mediated signaling, and signal transduction, producing reactive oxygen species and reactive nitrogen species and triggering programmed cell death. Additionally, mitochondria coordinate with other organelles to integrate and amplify diverse immune signals. In this review, we summarize recent advances in understanding how mitochondria function in plant immunity and how pathogens target mitochondria for host defense suppression. Pathogens have evolved different strategies to facilitate invasion of plants, including delivering enzymes and effector proteins to perturb mitochondrial morphology and functions. Mitochondria mediate the oxidative burst of reactive oxygen species and reactive nitrogen species for the activation of immune responses. Mitochondrial structural components, dynamics, and metabolism are closely associated with defense responses. Mitochondria are important in salicylic acid–mediated resistance and participate in the interplay among different hormones. Mitochondria mediate immune signal perception and amplification and play a central role in programmed cell death (PCD). Mitochondria cooperate with the chloroplast and nucleus in executing PCD and activating immune responses. [ABSTRACT FROM AUTHOR]