BACKGROUND: The relationship between dietary modification and Multiple Sclerosis (MS)-related disability has been emphasized in several researches. AIMS: To determine whether a co-administration of anti-inflammatory-antioxidant rich diet and synbiotics might improve clinical manifestations in progressive MS patients. METHODS: The study involved 70 patients with progressive MS (primary-progressive, secondary-progressive, and progressive-relapsing) who were randomized to receive either intervention (synbiotics capsule plus an anti-inflammatory-antioxidant-rich diet) or placebo. Quality of Life (QOL), Expanded Disability Status Scale (EDSS), and depression-anxiety scores were evaluated before and after the follow-up. Analysis of covariance was performed for final analysis (SPSS v.14). RESULTS: Significant reductions were seen in EDSS (2.6±1.1 to 2.4±1.0, P < 0.001), State Anxiety Inventory (53.7±10.3 to 47.8±10.6, P < 0.001), and QOL scores after four months of intervention. No significant difference was seen across the depression severity (Δ for intervention = –2.2±5.5 vs. Δ for control = –0.6±5.7; P = 0.264). CONCLUSION: This study demonstrates that a combination of synbiotics and diet could be a promising strategy to improve severity and clinical manifestations of progressive MS.