The effect of Micro-nano plastics (MNPs) is receiving attention in the marine environment because of their potential impact on marine organisms and humans. Future environmental hazards from these (MPs and NPs) pollutants cannot be neglected. The majority of the plastic trash discovered in the marine environment comes from land-based sources, and once plastic entered into the ocean, it can break down into smaller fragments and consumed by marine vertebrates and invertebrates directly or indirectly. Since these plastics have been discovered in microalgae, invertebrates like zooplankton and some benthonic creatures, vertebrates including fish and shellfish, seabirds, and amphibians, brine shrimp larvae and bivalves etc., assessing their toxicological effects on soil/marine sediments and aquatic life is a growing concern. Some marine vertebrates are impacted by MNPs, including birds, turtles (nutrient depletion) and whales (starvation). Small bits of plastic debris can be ingested by aquatic organisms, accumulating as they travel up the food chain and finally reaching humans. Marine vertebrates and invertebrates are important part of aquatic food chain and important as food, medicine, tourism for humans. Therefore, the chapter delineates impact of micro-nano plastics in vertebrates and invertebrates, which is being a major concern today.