Antimicrobial peptides (AMPs) may be the most promising substitute for antibiotics due to their effective antimicrobial activities and multiple function mechanisms against pathogenic microorganisms. In this study, a novel AMP containing 51 amino acids, named Lc1687, was screened from the large yellow croaker (Larimichthys crocea)viaaB. subtilissystem. Bioinformatics and circular dichroism (CD) analyses showed that Lc1687 is a novel anionic amphiphilic α-helical peptide, which was derived from the C-terminal of a Ferritin heavy subunit. The recombinant Lc1687 (named rLc1687) purified fromEscherichia coliexhibited strong activities against Gram-positive (Gram+) bacteriumStaphylococcus aureus, Gram-negative (Gram-) bacteriaVibrio vulnificus, V. parahaemolyticus, andScuticociliatida. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) revealed the possible function mechanisms of this peptide, which is to target and disrupt the bacterial cell membranes, including pore-forming, loss of fimbriae, and cytoplasm overflow, whereas gel retardation assay revealed that peptide Lc1687 cannot bind bacterial DNA. The peptide stability analysis showed that rLc1687 acts as a stable antimicrobial agent against Gram+ and Gram- bacteria at temperatures ranging from 25 to 100°C, pH 3-12, and UV radiation time ranging from 15 to 60 min. A hemolytic activity assay confirmed that this peptide may serve as a potential source for clinical medicine development. Taken together, Lc1687 is a novel AMP as it is a firstly confirmed Ferritin fragment with antimicrobial activity. It is also a promising agent for the development of peptide-based antibacterial and anti-parasitic therapy.