Abstract Self‐monitoring in tumor therapy is a concept that allows for real‐time monitoring of the location and state of applied nanomaterials. This monitoring relies on dynamic signals, such as wave or magnetic signals, which vary in response to changes in the location and state of nanomaterials. Dynamic changes in nanomaterials can be monitored using dynamic signals, making it possible to determine and control the treatment process. Theranostic nanomaterials, which possess unique physical and chemical properties, have recently been explored as a viable option for self‐monitoring. With the help of self‐monitoring, theranostic nanomaterials can guide themselves to achieve region‐selective treatment with higher controllability and safety. In this review, self‐monitoring theranostic nanomaterials will be introduced in three parts according to their roles during therapy: tumor accumulation, tumor therapy, and metabolism. The limitations and future challenges of current self‐monitoring theranostic nanomaterials will also be discussed.