This review article discusses the design and fabrication of magnetic nanoparticles (MNPs) for targeted drug delivery and imaging. MNPs, particularly superparamagnetic iron oxide nanoparticles (SPIONs), have gained significant attention due to their magnetic properties, which enable them to be used in magnetic resonance (MR) imaging. The article highlights the importance of proper design criteria, including size, coating, and molecular functionalization, to enhance the performance of MNPs in vivo. It also reviews the physicochemical properties and surface modifications that can improve MNP management of biological barriers, such as the blood-brain barrier (BBB). The article further explores the challenges and strategies involved in directing MNPs to specific tissues through passive, active, and magnetic targeting approaches. Additionally, it discusses the drug loading and release mechanisms of MNPs, as well as the toxicity considerations. The fabrication techniques for core MNPs and their surface coatings, including poly(ethylene glycol) (PEG), dextran, chitosan, polyethyleneimine (PEI), liposomes, and micelles, are detailed. The article concludes with a discussion on surface modification chemistry, including covalent linkages, click chemistry, and linker chemistry, to conjugate targeting, therapeutic, and imaging reporter molecules to MNPs.This review article discusses the design and fabrication of magnetic nanoparticles (MNPs) for targeted drug delivery and imaging. MNPs, particularly superparamagnetic iron oxide nanoparticles (SPIONs), have gained significant attention due to their magnetic properties, which enable them to be used in magnetic resonance (MR) imaging. The article highlights the importance of proper design criteria, including size, coating, and molecular functionalization, to enhance the performance of MNPs in vivo. It also reviews the physicochemical properties and surface modifications that can improve MNP management of biological barriers, such as the blood-brain barrier (BBB). The article further explores the challenges and strategies involved in directing MNPs to specific tissues through passive, active, and magnetic targeting approaches. Additionally, it discusses the drug loading and release mechanisms of MNPs, as well as the toxicity considerations. The fabrication techniques for core MNPs and their surface coatings, including poly(ethylene glycol) (PEG), dextran, chitosan, polyethyleneimine (PEI), liposomes, and micelles, are detailed. The article concludes with a discussion on surface modification chemistry, including covalent linkages, click chemistry, and linker chemistry, to conjugate targeting, therapeutic, and imaging reporter molecules to MNPs.