The PI3K-AKT-mTOR pathway is a crucial signaling network dysregulated in many cancers, promoting cell survival, growth, and proliferation, and often implicated in resistance to cancer therapies. Inhibition of this pathway by PI3K inhibitors disrupts a complex network of cellular processes that contribute to breast cancer, markedly reducing cell proliferation, promoting apoptosis, inhibiting angiogenesis, and ultimately preventing tumor formation and progression. In hormone receptor–positive (HR+), activating PIK3CA mutations occur in approximately 35% to 40% of patients and a variable prevalence across BC subtypes. Testing is thus crucial to ensure appropriate treatment selection. The development of PI3K-targeted agents may revolutionize the treatment landscape for HR+, HER2- metastatic breast cancer (mBC, and due to the recent approval of inavolisib, clinicians must be apprised of both the clinical evidence and best practices regarding the use of this agent. This activity has been designed to review the role of the PI3K-AKT-mTOR pathway in breast cancer, the importance of testing when making clinical decisions, and the role of PI3K-targeted therapies in HR+, HER- mBC.