Background. Lumbar disc herniation (LDH) is the most common diagnosed degenerative pathology in the lumbar spine. Because of its role in spinal stability there is an increased interest in the role of the Lumbar Multifidus muscle in low back pain research. Despite surgical treatment long-term, disability and pain remain a persistent problem. The aim of the study is to compare side-to-side Lumbar Multifidus muscle fibre characteristics in unilateral LDH patients, and compare both sides to a healthy control group. Methods. Thirty patients (n = 17 men and n = 13 women) scheduled for microdiscectomy for unilateral disc herniation and ten healthy controls (n = 5 men and n = 5 women) were included in this study. Biopsies of the Lumbar Multifidus muscle were analysed by means of immunohistochemistry combined with immunofluorescence microscopy to determine type I and type II muscle fibre type distribution, cross-sectional area, myonuclear-and satellite cell content, inflammation and various indices of muscle fibre capillarisation. Results. The proportion of muscle fibres with centrally located myonuclei, various indicis of muscle fibre capillarisation and pro-and anti-inflammatory cell content were higher in the patients compared with the healthy controls. No differences were observed in type I and type II muscle fibre characteristics between the injured and uninjured side within the LDH patients. Conclusions. This study shows clear differences in Lumbar Multifidus muscle fibre characteristics between LDH patients, irrespective of injured or uninjured side, and healthy controls. Additional studies are warranted to establish the clinical significance of these differences in muscle fibre morphology in LDH compared with healthy controls. Study registration. This trial was registered on ClinicalTrials.gov under the identification number NCT03753711.