Delivering drugs to the brain has historically been a difficult task due to the impermeability of the blood-brain barrier (BBB) and the brain endothelial cells (BECs), which make up the walls of the blood vessels in the central nervous system (CNS). Despite immense efforts to circumvent the BBB, several non-invasive brain drug delivery methods have emerged, such as focused (FUS) and scanning (SUS) ultrasound, nanocarriers, and receptor-mediated transcytosis (RMT). Although these techniques have yet to be FDA approved, RMT offers a unique opportunity for drug delivery, as receptors already expressed on the BBB pose as targets for large drug complexes to enter the brain through endocytosis. One of the most targeted receptors for RMT is the transferrin receptor (TfR), which naturally transports extracellular iron to the brain by binding its natural ligand, transferrin, which carries iron molecules. In comparison to other possible BBB targets, TfR holds great promise due to its relatively consistent expression throughout age and disease progression, ability to be targeted without interfering with its normal function, and its high internalization rate in the brain. This critical literature review discusses several methods for brain drug delivery, highlighting the future potential and remaining challenges RMT faces.