Breast cancer is the most diagnosed cancer worldwide, with rising incidence rates globally. Early detection is essential for improving survival rates, yet conventional imaging methods have limitations. Mammography, the gold standard, struggles with reduced sensitivity in dense breast tissue. Ultrasound (US) aids in distinguishing lesions but is highly operator-dependent, while MRI offers detailed imaging but remains costly and less accessible. These challenges underscore the need for improved imaging technologies. Photoacoustic imaging (PAI) is an emerging, noninvasive modality that integrates optical and ultrasound imaging to provide high-resolution, real-time visualization of breast tissue. Unlike conventional methods, PAI enables the assessment of tumor vascularization, blood oxygenation, and molecular characteristics, enhancing early cancer detection and treatment monitoring. Various PAI techniques, including photoacoustic tomography, photoacoustic microscopy, multispectral PAI, and photoacoustic endoscopy, offer unique advantages in imaging tumor structure and function. Recent advancements, such as molecular contrast agents and multimodal integration with ultrasound and MRI, further enhance PAI’s diagnostic accuracy. This chapter explores the principles, techniques, and applications of PAI in breast cancer detection, tumor characterization, and therapy assessment. We also address challenges in clinical translation and future prospects. With continued development, PAI has the potential to revolutionize breast cancer diagnostics and improve patient outcomes.