Background: Multiple sclerosis (MS) is a long-term condition in which the immune system attacks the brain and spinal cord, affecting approximately 2.9 million people worldwide. Among the dietary patterns studied in MS, the Mediterranean diet has attracted the most research attention for its potential to reduce inflammation and slow the progression of disability. Objective: This study used a survey-based approach to collect data from one hundred MS patients across three countries – Slovakia, Italy, and the United Kingdom/international cohort to explore the association between disability levels, Mediterranean diet adherence, and disease duration. The main aim was to examine how Expanded Disability Status Scale (EDSS) scores and length of time living with MS were associated with how closely patients followed the Mediterranean diet. Secondary aims included looking at how often patients consumed specific food groups, whether they were taking vitamin D or omega-3 supplements, whether their eating habits had changed since their MS diagnosis, and how many patients had received formal nutrition advice from their healthcare team, with results broken down by country and level of disability. Material and Methods: This cross-sectional study explored the relationship between disability level, Mediterranean diet adherence measured using the validated 14-item Mediterranean Diet Adherence Screener (MEDAS), and disease duration in 100 MS patients from Slovakia (n=47), Italy (n=36), and a UK/International cohort (n=17). Results: The overall mean MEDAS score was 3.96 ± 2.26, reflecting predominantly poor dietary adherence across the entire sample: 77% of patients fell into the low-adherence range (score 0-5), 22% into the moderate range (6-9), and only one patient (1%) reached high adherence (10-14). MEDAS scores were highest in patients with the lowest disability (mean 4.73 at EDSS 0-2) and declined across higher EDSS groups, with the proportion of low-adherence patients rising from 63.6% at EDSS 0-2 to 90.0% at EDSS 6-8. Vegetable consumption, the most important food component of the Mediterranean diet, declined modestly from 4.64 to 4.33 times per week across the disability spectrum. Regarding disease duration, the lowest mean MEDAS scores were observed in patients diagnosed for 1-5 years (3.75) and those living with MS for 20 or more years (3.69), the latter group also showing the highest rate of low adherence (85.7%). Italian patients had the highest mean MEDAS score (4.56), compared with 4.12 in the UK/international group and 3.45 in Slovakia. A notable discrepancy was found between the 24% of patients who self-identified as following the Mediterranean diet and the objective MEDAS results, in which only one patient achieved high adherence. Only 26% of patients had received formal dietary advice from their doctor, despite 47% having changed their eating habits independently after diagnosis. Conclusions: These findings show that higher disability and longer disease duration are both linked to poorer Mediterranean diet adherence when assessed with a validated tool and highlight the need to include structured nutritional support as a regular part of MS care.