Owing to unique facets, such as large surface area, tunable synthesis parameters, and ease of functionalization, mesoporous silica nanoparticles (MSNs) have transpired as a worthwhile platform for cancer theranostics over the last decade. The full potential of MSNs in cancer theranostics, however, is yet to be realized. While MSNs can be employed for targeted drug delivery and imaging, their effectiveness can frequently be hindered by factors, such as biological barriers, complex tumor microenvironment, target non-specificity and ineffectiveness of individual functionalized moieties. The primary purpose of this review is to highlight technological advances such as tumor-specific, stimuli-responsive “smart” MSNs and multimodal MSN-based hybrid nanoplatforms that have the potential to overcome these limitations and improve MSN effectiveness in cancer theranostics. This article offers an extensive overview of MSN technology in cancer theranostics, outlining key directions for future research as well as the challenges that are involved in this aspect. We aim to underline the vitality of MSN technology and the relevance of current research and advancements in this field to potentially enhance clinical outcomes through the provision of more precise and focused theranostic approaches.