Endophytic bacteria are the endosymbionts that live inside the host plant at least for a part of its life cycle without causing apparent disease. In most of the plant species, endophytic bacteria are actively colonizing plant tissues locally as well as systemically. It may include both gram-positive and gram-negative bacteria with diverse morphology. Bacterial endophytes can be found in various sites of the plants like root, leave, stem and seed. In a single plant, more than one type of bacterial endophytes can be seen. Usually, the endosymbiont gives some beneficial effects to the host plants. Most of the endosymbiont help the host in resisting the environmental stress and also help to resist the pathogens. When compared to rhizospheric bacteria, endophytic bacteria have more advantage as they can stay in direct contact with the plant tissues. Some endophytes produce various extracellular enzymes, antimicrobial substances and some plant-growth-promoting hormones. This review mainly focuses on the endophytic bacteria that are associated with various host plants and their biological activities. © 2020 World Research Association. All rights reserved.