The appreciable development in nanotechnology has drawn the attention of several researchers cutting across different fields. However, some nanoparticles have been identified to possess harmful effects on humans and the environment. Hence, putting these cause and effect patterns into context is highly required for future research and discussions about nanotechnology. This study reviewed existing literature on the toxicity and cytotoxicity effects of some nanoparticles to compare reaction patterns. Many kinds of research used different cell cultures, including cancer cell lines, human endothelial cells, hepatic cells, which were tested both in vitro and in vivo to check the mechanism of the possible toxicity effects. Adverse effects of nanoparticles identified involved damaged DNA leading to mutations and generation of reactive oxygen species (ROS). The prominent identified common toxicity responses in nanoparticle-cell interaction were lysosomes formation interference, necrosis and apoptosis, nanoparticles and protein interaction, and agglomerate formation in other body parts. Some reports showed that the causes of these responses might be due to the physicochemical properties of the interrogated particles, such as particle size, shape, surface functionalisation, surface charge. Furthermore, nanoparticles’ toxicity effects are both concentration-dependent and time-dependent, highly pronounced in chemical or physical-based synthetic routes. Cytotoxic effects of nanoparticles were mainly linked to their synthetic method, nature of the reducing agent, and culture media.