Information regarding the epidemiology of spasticity in patients with multiple sclerosis (MS) in Spain is limited. This cross-sectional survey-based study was undertaken to evaluate the symptoms, severity and consequences of MS-related spasticity (MSS) and to estimate the prevalence of MSS overall and according to the degree of severity (mild/moderate/severe). Adult MS patients (n = 8463) from the two main Spanish MS patients' associations were asked to complete a web-based questionnaire. Two thousand six hundred twenty seven responses were received, of which 2029 were valid for analysis. Two thirds were for women. The mean age of respondents was 40.2 years and the mean MS duration was 8.7 years. MSS was reported by 65.7% of respondents with 40% of these rating it as moderate/severe. MS patients with spasticity experienced more symptoms (including greater difficulty walking), consumed more healthcare resources (including care and rehabilitation sessions), and had a higher degree of disability than patients without spasticity. There was a significant correlation between increasing severity of spasticity and worsening of symptoms. Only 42.4% of patients with moderate spasticity and 52.6% of patients with severe spasticity were currently receiving antispasticity medication compared with 69% and 79%, respectively, reported in a similar survey-based study from the United States; this is likely to reflect regional variations in practice. Early and effective treatment of MSS is important to minimise the consequences of spasticity-related symptoms on patients' quality of life and the economic burden on healthcare systems. In appropriate patients, antispastic treatment, including pharmacotherapy and physiotherapy/rehabilitation, may provide such benefits.