Magnetic nanoparticles (MNPs) are attracting significant attention due to their unique magnetic properties and potential applications in biomedical fields. Recent advancements in nanotechnology have enhanced the ability to tailor MNPs for specific biomedical uses, such as MRI contrast agents and drug delivery systems. MNPs with higher magnetic moments, non-fouling surfaces, and increased functionalities are being developed to address clinical needs in cancer, cardiovascular disease, and neurological disorders. The incorporation of targeting agents and functional ligands, such as fluorophores and permeation enhancers, has significantly improved the applicability and efficacy of MNPs. MNPs can enhance proton relaxation and serve as MRI contrast agents, providing high-resolution anatomical images. Superparamagnetic iron oxides (SPIOs) have been widely used in clinical settings for bowel and liver/spleen imaging. Ultrasmall superparamagnetic iron oxides (USPIOs) are also under clinical trial for lymph node metastasis detection. As therapeutic tools, MNPs have been evaluated for targeted drug delivery through magnetic drug targeting (MDT) and active targeting. These techniques aim to overcome the limitations of systemic distribution of conventional chemotherapies by directing therapeutic agents to specific disease sites, reducing dosage, and minimizing side effects. The behavior of MNPs in vivo is a significant challenge, as they can be recognized and cleared by the reticuloendothelial system (RES) before reaching target tissues. Their fate depends on size, morphology, charge, and surface chemistry, which affect their pharmacokinetics and biodistribution. Techniques such as reducing size and grafting non-fouling polymers have been employed to improve stealthiness and increase blood circulation time. Next-generation MNPs incorporate novel nanocrystalline cores, coating materials, and functional ligands to enhance detection and specific delivery. Iron oxide, metallic, and bimetallic MNPs are being developed with improved magnetic properties and stability. Surface coatings, including polymeric, liposomal, and core-shell structures, are crucial for preventing agglomeration and opsonization, and for functionalization with targeting agents and therapeutic agents. Pharmacokinetics and biodistribution studies highlight the importance of particle size, shape, charge, and surface chemistry in determining blood half-life and accumulation in target tissues. Passive targeting through the enhanced permeability and retention (EPR) effect and active targeting through receptor-ligand interactions are key strategies for improving accumulation in diseased tissues. MR imaging applications of MNPs include cancer and cardiovascular disease imaging. MNPs provide contrast enhancement by shortening both longitudinal and transverse relaxation times, with superparamagnetic nanoparticles typically used for T2-weighted imaging. MNPs have shown promise in improving tumor detection, diagnosis, and therapeutic management, as well as in cardiovascular disease imaging and evaluation of atherosclerotic lesions. Overall, the review provides an overview of the recent developments in MNP technology and their applications in MR imaging and drug delivery, highlighting the potential of MNPs to revolutionMagnetic nanoparticles (MNPs) are attracting significant attention due to their unique magnetic properties and potential applications in biomedical fields. Recent advancements in nanotechnology have enhanced the ability to tailor MNPs for specific biomedical uses, such as MRI contrast agents and drug delivery systems. MNPs with higher magnetic moments, non-fouling surfaces, and increased functionalities are being developed to address clinical needs in cancer, cardiovascular disease, and neurological disorders. The incorporation of targeting agents and functional ligands, such as fluorophores and permeation enhancers, has significantly improved the applicability and efficacy of MNPs. MNPs can enhance proton relaxation and serve as MRI contrast agents, providing high-resolution anatomical images. Superparamagnetic iron oxides (SPIOs) have been widely used in clinical settings for bowel and liver/spleen imaging. Ultrasmall superparamagnetic iron oxides (USPIOs) are also under clinical trial for lymph node metastasis detection. As therapeutic tools, MNPs have been evaluated for targeted drug delivery through magnetic drug targeting (MDT) and active targeting. These techniques aim to overcome the limitations of systemic distribution of conventional chemotherapies by directing therapeutic agents to specific disease sites, reducing dosage, and minimizing side effects. The behavior of MNPs in vivo is a significant challenge, as they can be recognized and cleared by the reticuloendothelial system (RES) before reaching target tissues. Their fate depends on size, morphology, charge, and surface chemistry, which affect their pharmacokinetics and biodistribution. Techniques such as reducing size and grafting non-fouling polymers have been employed to improve stealthiness and increase blood circulation time. Next-generation MNPs incorporate novel nanocrystalline cores, coating materials, and functional ligands to enhance detection and specific delivery. Iron oxide, metallic, and bimetallic MNPs are being developed with improved magnetic properties and stability. Surface coatings, including polymeric, liposomal, and core-shell structures, are crucial for preventing agglomeration and opsonization, and for functionalization with targeting agents and therapeutic agents. Pharmacokinetics and biodistribution studies highlight the importance of particle size, shape, charge, and surface chemistry in determining blood half-life and accumulation in target tissues. Passive targeting through the enhanced permeability and retention (EPR) effect and active targeting through receptor-ligand interactions are key strategies for improving accumulation in diseased tissues. MR imaging applications of MNPs include cancer and cardiovascular disease imaging. MNPs provide contrast enhancement by shortening both longitudinal and transverse relaxation times, with superparamagnetic nanoparticles typically used for T2-weighted imaging. MNPs have shown promise in improving tumor detection, diagnosis, and therapeutic management, as well as in cardiovascular disease imaging and evaluation of atherosclerotic lesions. Overall, the review provides an overview of the recent developments in MNP technology and their applications in MR imaging and drug delivery, highlighting the potential of MNPs to revolution