Onychomycosis is a fungal nail infection that causes nail discoloration, nail plate thickening, and onycholysis. Efinaconazole 10% topical solution is an FDA-approved treatment for onychomycosis patients aged 6 years and above. The drug functions as an antifungal by disrupting ergosterol synthesis in the fungal cell membrane. It exhibits higher in vitro activity against dermatophytes than other available antifungals such as ciclopirox and itraconazole, and the activity is comparable to amorolfine and terbinafine. Efinaconazole also provides enhanced nail penetration compared with other topical antifungals due to low surface tension, poor water solubility, and low keratin affinity. The pharmacokinetic studies suggest that the efinaconazole topical delivery to the nail bed is not markedly affected by the presence of disease. There is a subset of onychomycosis patients who are more likely to respond to efinaconazole 10% solution: female patients, those with lower BMI, mild onychomycosis, a short disease duration, no infected non-target toenails (large toenail disease only), and when concomitant tinea pedis is treated. Experts recommend efinaconazole 10% topical solution as the first line for mild-to-moderate onychomycosis, pediatric onychomycosis, those with liver or kidney disease, and as maintenance therapy to prevent relapse. The side effects of topical efinaconazole are minimal: most commonly ingrown toenails, dermatitis, vesicles, and pain at the application site. Altogether, phase I and phase III clinical trials, and post-hoc analyses indicate that efinaconazole 10% topical solution is a safe and effective treatment for adult and pediatric onychomycosis, with a satisfactory mycological and clinical cure.