Increasing nanomedicinal approaches have been developed to effectively inhibit tumor growth; however, critical questions such as whether a nanomedicinal approach can mitigate latent side effects are barely addressed. To this end, we established a zebrafish xenograft tumor model, combining pseudodynamic three-dimensional cardiac imaging and image analysis to enable simultaneous and quantitative determination of the change of tumor volume and cardiac function of zebrafish upon specific nanoformulation treatment. Doxorubicin (DOX), a well-known chemotherapeutic agent with cardiotoxicity, and a recently developed DOX-loaded nanocomposite were employed as two model drugs to demonstrate the effectiveness to utilize the proposed evaluation platform for rapid validation. The nanoformulation significantly mitigated DOX-associated cardiotoxicity, while retaining the efficacy of DOX in inhibiting tumor growth compared to administration of carrier-free DOX at the same dose. We anticipate that this platform possesses the potential as an efficient assessment system for nanoformulated cancer therapeutics with suspected toxicity and side effects to vital organs such as the heart.