Nanotechnology has emerged as a promising field in cancer theragnostics, offering novel approaches for early detection, targeted drug delivery, and personalized treatment. Core-shell nanoconstructs, in particular, have garnered significant attention due to their unique structural and functional properties that enable enhanced specificity, efficiency, and versatility in cancer management. The integration of advanced imaging techniques, such as quantum dots and gold nanoparticles, further enhances the diagnostic capabilities of core-shell nanoconstructs, enabling real-time monitoring and precise evaluation of their therapeutic potential. This chapter provides a comprehensive overview of the characterization and evaluation techniques employed to assess the performance of core-shell nanoconstructs for cancer theragnostics. Techniques such as electron microscopy, spectroscopy, dynamic light scattering, and zeta potential analysis are discussed for structural and morphological characterization. Additionally, advanced imaging methods like fluorescence imaging, MRI, and PET/CT are explored for their role in evaluating the in vivo diagnostic potential of these constructs. This chapter also discusses the various analytical methods used to assess the physicochemical properties, targeting capabilities, drug loading and release kinetics, and in vitro and in vivo efficacy of these nanoplatforms. The integration of these characterization techniques enables the development of highly efficient and safe nanoconstructs for cancer diagnosis and treatment, paving the way for personalized and precision oncology. Finally, this chapter explores the challenges and considerations in characterizing and evaluating core-shell nanoparticles.