Cementitious materials play a crucial role in construction but are highly susceptible to microcracking, which affects their durability, increases maintenance costs, and poses environmental challenges. Microbial-induced calcite precipitation (MICP) has emerged as a promising self-healing solution to address these issues by utilizing bacteria’s natural ability to autonomously repair cracks, thereby enhancing the longevity and sustainability of concrete structures. This review explores microbial loading techniques and immobilization materials designed to optimize the self-healing capabilities of cementitious systems. It discusses the role of bacterial species such as Bacillus megaterium and Bacillus licheniformis in calcium carbonate precipitation to seal cracks. The paper also reviews key immobilization methods such as encapsulation, microencapsulation, adsorption, and matrix entrapment, highlighting their effects on bacterial survival, bioactivity, and long-term stability in concrete. Additionally, the review covers the use of various supporting materials like natural fibers, biopolymers, hydrogels, and inorganic matrices, which act as effective carriers for bacterial immobilization. Natural fibers are particularly emphasized for their eco-friendliness, biodegradability, and ability to improve both microbial activity and the mechanical properties of cementitious composites. The challenges related to material degradation, compatibility with cement matrices, and scalability of these technologies are critically analyzed. The review concludes by identifying research gaps and offering recommendations for future studies to enhance the performance of microbial loading and immobilization systems, making concrete more sustainable, durable, and cost-efficient.