Regenerative medicine-based approaches for caries treatment focus on biomimetic remineralization of initial carious lesions as a minimal invasive therapy. In vitro, self-assembling peptide P-4 enhances remineralization of early carious lesions. To investigate the safety and clinical efficacy of P-4 for treatment of initial caries, a randomized controlled single-blind study was conducted on children aged >5 y with visible active early caries on erupting permanent molars. Subjects were randomized to either the test group (P-4 + fluoride varnish) or control group (fluoride varnish alone). Caries were assessed at baseline and at 3 and 6 mo posttreatment per laser fluorescence, a visual analog scale, the International Caries Detection and Assessment System, and Nyvad caries activity criteria. Intention-to-treat analyses were performed, and safety and clinical feasibility of the treatment approaches were assessed. Compared with the control group, the test group showed clinically and statistically significant improvement in all outcomes at 3 and 6 mo. The laser fluorescence readings (odds ratio = 3.5, P = 0.015) and visual analog scale scores (odds ratio = 7.9, P < .0001) were significantly lower for the test group, and they showed regression in the International Caries Detection and Assessment System caries index (odds ratio = 5.1, P = 0.018) and conversion from active to inactive lesions according to Nyvad criteria (odds ratio = 12.2, P < 0.0001). No adverse events occurred. The biomimetic mineralization facilitated by P-4 in combination with fluoride application is a simple, safe, and effective noninvasive treatment for early carious lesions that is superior to the presently used gold standard of fluoride alone. By regenerating enamel tissue and preventing lesion progression, this novel approach could change clinical dental practice from a restorative to a therapeutic approach. This could avoid additional loss of healthy hard tissue during invasive restorative treatments, potentially enabling longer tooth life and thereby lowering long-term health costs ( ClinicalTrials.gov NCT02724592).