A Gram-stain-positive, aerobic, motile, non-spore-forming and rod-shaped actinobacterium, designated strain 4Q3S-7, was isolated from a piece of surface-sterilized bark of Kandelia candel collected at the Cotai Ecological Zone in Macao, China. Colonies were yellowish white, circular, smooth and convex. The 16S rRNA gene sequence of strain 4Q3S-7 exhibited highest similarities to Marmoricola ginsengisoli Gsoil 097 (97.6%), Marmoricola solisilvae KIS18-7 (97.6%) and Marmoricola pocheonensis Gsoil 818 (97.3145). Phylogenetic analysis showed that strain 4Q3S-7 clustered with species of the genus Marmoricola and was clearly affiliated to the genus Marmoricola. Genomic analyses, including average nucleotide identity and DNA-DNA hybridization, clearly separated strain 4Q3S-7 from M. ginsengisoli Gsoil 097, M. solisilvae KIS18-7 and M. pocheonensis Gsoil 818 with values below the thresholds for species delineation. Strain 4Q3S-7 had LL-2,6-diaminopimelic acid as the diagnostic diamino acid in the cell wall. The major fatty acids (>10% of total fatty acids) were C10-methyl (TBSA), Cω9c, iso-Cand iso-C2-OH. The predominant menaquinone was MK-8(H). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol and an unidentified phospholipid. The DNA G+C content of strain 4Q3S-7 was 72.0 mol% (draft genome sequence). Based on its phylogenetic, phenotypic and chemotaxonomic features, strain 4Q3S-7 is considered to represent a novel species of the genus Marmoricola, for which the name Marmoricola mangrovicus sp. nov. is proposed. The type strain is 4Q3S-7 (=KCTC 39790=CGMCC 4.7424).