Strain SB0023/3 T, isolated from spores of the arbuscular mycorrhizal fungus Glomus iranicum var. tenuihypharum, was analysed to determine whether it represents a new species. It was studied for its applicability in the field of agriculture to reduce the input of nitrogen fertilizers. Comparative analysis of the 16S rRNA gene sequence shows the strain to be affiliated to the genus Methylobacterium, the closest similarities (98.7%) being shared with Methylobacterium dankookense. Further phylogenomic analysis through Up-to-date Bacterial Core Gene (UBCG) confirmed Methylobacterium dankookense as its closest relative. Average Nucleotide Identity (ANI) and in silico DNA-DNA hybridization (DDH) were lower than 92% and 44%, respectively, of the values shown by its phylogenetic relatives. Its genome had an approximate length of 6.05 Mb and the G + C content of the genome was 70.1 mol%. The main cellular fatty acid was Summed Feature 8 (C18:1ω7c and/or C18:1ω6c). It is a Gram-staining-negative, pink-pigmented, strictly aerobic and facultative methylotroph; it grows at 28 ºC and can grow at up to 3% salinity in the presence of sodium chloride. All the data collected support the naming of a novel species to accommodate the strain SB0023/3 T, for which the name Methylobacterium symbioticum sp. nov. is proposed. The type strain is SB0023/3 T (=CECT 9862 T =PYCC 8351 T).