Alzheimer's Disease (AD) is a complex and progressive neurodegenerative disease, and the most common cause of dementia usually occurs due to old age. Production and accumulation of amyloid-β peptide (Aβ) represent the major pathological event of the disease. The formation of amyloid- β results due to proteolytic cleavage of amyloid precursor protein (APP) by beta-site amyloid precursor protein cleaving enzyme (BACE1) shown as the amyloid hypothesis, a prevalent theory for AD pathogenesis. Thus, BACE1 represents a novel target to decrease cerebral Aβ concentration and slow down the disease's progression. The structure-based drug design approach led to a wide variety of small molecules with the mechanism of action centered around inhibition of β-secretase protease (BACE1), which are shown to have drug-like properties and reduce brain Aβ levels. Based on transition state isosteres, BACE1 inhibitors can largely be classified as peptidomimetics and non-peptidomimetics. The subclasses of the two categories have been covered with different scaffolds like statin, norstatin, carbinamine, hydroxyethylene, hydroxyethylamine, acyl guanidine, 2- aminopyridine, aminoimidazole, aminohydantoin, aminothiazoline, aminooxazoline, aminoquinoline, piperazine-based. Among these small molecules, those who fulfilled general requirements for a drug aimed at the central nervous system (CNS) and selectivity over other aspartyl proteases reached the final pipeline of clinical trials. Here, in this review, we summarize the journey of BACE1 inhibitors through different practices of drug design development, Structural Activity Relationship (SAR), and other inhibitor candidates that are currently in clinical trials as BACE1 inhibitors.