<p>Advanced breast cancer, a prevalent and deadly disease, requires innovative approaches for effective diagnosis and treatment. Mesoporous silica nanoparticles (MSNs) have emerged as a versatile platform for theranostics, a field that integrates therapeutic and diagnostic functions within a single system to enable precise, personalized medical care. MSNs are valued for their high surface area, ordered pore structure, excellent biocompatibility, and customizable particle and pore sizes. These features make MSNs ideally suited to theranostics. This review explores the latest advancements in the application of MSNs in breast cancer theranostics. The unique structural and functional properties of MSNs are mediated by their surface modifications, as well as their role in enhancing drug delivery, improving imaging capabilities, and providing targeted therapies. The integration of specific imaging modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), computed tomography (CT), photoluminescence (PL), ultrasound (US), photoacoustic imaging (PAI), and fluorescence imaging (FL), with therapeutic agents, including chemotherapeutic drugs and photosensitizers, is discussed in detail. Additional applications for theranostic MSNs are considered, including the development of targeted delivery systems for primary and metastatic diseases to optimize breast cancer treatment. The challenges and prospects of MSN-based theranostic systems, including biocompatibility and clinical translation, are also addressed. In summary, this review highlights the potential of MSNs as a multifunctional delivery platform, enabling personalized treatment strategies for managing breast cancer.</p> Graphical Abstract <p></p>