Cancer, one of the most dangerous diseases with a high mortality rate, has attracted much attention and interest. Advances in tissue engineering and microfluidics have led to the development of tumor-on-chips (TOCs) capable of in-vitro modeling the dynamic microenvironment, growth, and inter-cellular interactions of tumor tissues, providing a promising platform for oncology research. The search for powerful analytical tools for TOCs has facilitated the integration of electrochemical biosensors due to their high sensitivity and selectivity, low cost, portability, ease of fabrication, and low sample consumption. Recent reports have demonstrated promising applications of integrated electrochemical biosensors in cancer research at cellular and molecular levels in TOCs. In this review, we will introduce TOCs that model different stages of the tumor and highlight the use of electrochemical biosensors for the analysis of tumor cells and biomarkers. Future work may focus on the development of flexible and robust electrochemical biosensors with high mechanical compliance with tumor tissues for long-term monitoring of the tumor microenvironment.