Cancer, a combination of haematological and neoplastic malignancies, is a dreadful disease accounting for major fatalities worldwide. The domain of innovative nanoparticle-based technology has revolutionized the field of cancer therapeutics and imaging. With an emphasis on various nano-immunotherapeutic approaches, this study highlights the most recent developments in nano-immune engineering for metastatic tumours. Nanotechnology-based cancer immunotherapy has powered the (i) activation of T-cells in the tumour microenvironment (TME), (ii) preparation of efficient nanovaccines via nano-carriers and (iii) generation of smart nanomaterials which change their size/shape (size range of 1 to 1000 nm) and functionality upon activation in TME. The tumour microenvironment has an important, albeit contentious, role in controlling nanoparticle (NP) dispersion and subsequent biological consequences. The current study promotes the harnessing of potential peripheral immune cells by avoiding the creation of a pre-metastatic niche and, thus, suppressing tumour recurrence. This review descriptively accounts for a wide array of nanomaterials based on their polymeric constituents. Moreover, the current article explores the obstacles of integrating nanoscale immunomodulators and presents a forward-looking view of the novel nanotechnology-based approaches that may eventually prove helpful in eliminating metastatic illnesses.