Aim: The study aimed to investigate and compare the remineralization potential of Lithothamnion calcareum and Lithothamnion superpositum on tooth enamel with commercially available casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF). Materials and methods: A total of 30 human third molars indicated for extraction was chosen for this study. Carious lesions depicting the early stages of tooth subsurface enamel lesions were produced by immersing tooth samples in a demineralization bath for 72 hours. The samples were divided into three groups of 10 each. Group I (control): CPP-ACPF, group II: Lithothamnion calcareum, and group III: Lithothamnion superpositum. The teeth were immersed in their respective solutions and the samples were then kept in a thermobath for 21 hours for 7 days following which they were then tested by Vickers microhardness test and X-ray fluorescence spectroscopy. Results: Group II—Lithothamnion calcareum, exhibited a better remineralization potential of (224.35) than group III—Lithothamnion superpositum (215.64). Nonetheless, the commercial agent, a group I (CPP-ACPF), displayed the most efficiency in remineralizing tooth enamel. Conclusion: Among the alternative potential remineralizing samples tested, group II—Lithothamnion calcareum, exhibited maximum remineralization potential value followed by other algae but was not to the extent of the commercially available CPP-ACPF. The results of this study with regard to the alternative tooth-enamel remineralizing samples tested, were promising. Clinical significance: The alternative, a tooth-enamel remineralizing agent will serve as a natural and economical option for all sections of society, especially in rural India. © 2023 Elsevier B.V., All rights reserved.