OBJECTIVES: Albeit effectiveness of subcutaneous treatments for Multiple Sclerosis (MS) has been demonstrated, adverse reactions and pain may entail problems regarding treatment satisfaction and continuity. This study aims to adapt and validate the Spanish version of the “Multiple Sclerosis Treatment Concerns Questionnaire-MSTCQ”, which evaluates satisfaction with the injection device (ID) in 4 dimensions: Injection system (A), Side-effects (B) (flu-like symptoms, reactions, and satisfaction), Treatment experience (C) and Benefits (D).  METHODS: Two Stages: 1)Cultural adaptation: Forward-backward translation and expert (n=6) and patient (n=30) panels; 2)Validation: Observational, cross-sectional, multicenter study. 143 adult patients suffering from MS and using an ID were evaluated. Tools employed: MSTCQ, Patient-Reported Indices for Multiple Sclerosis (PRIMUS), Treatment Satisfaction Questionnaire for Medication (TSQM), Morisky Green and Patient Injection Site Reaction (ISR) and Injection Site Pain (ISP). Psychometric properties: Feasibility (% valid cases and ground/ceiling effects); Reliability (Cronbach α) and test-retest (41 patients, Intraclass Correlation Coefficient, ICC); as well as construct (Factorial analysis of dimensions A and B, FA) and convergent (Spearman MSTCQ vs. TSQM) validity. RESULTS: Mean age(SD) in cases was 41,94(10,47) years, 63% female, 88,11% suffering from Relapsing-Remitting MS. MSTCQ feasibility was adequate (missing 0%-2,80%). High internal consistency, total score (A+B) α =0, 89, by dimensions α (A, B and C): 0,76, 0,89 and 0,92, respectively. Furthermore, a concordance was found between total (ICC= 0, 98) and by dimensions ICC (A, B and C) scores: 0,82, 0,97 and 0,89, respectively. The FA confirms dimensions A and B from the original questionnaire. Lastly, the association between total and by dimensions scores, from MSTCQ and TSQM was, overall, moderately strong (Rho between-0, 74, y 0, 42) and significant (p<0,05; p<0,01). CONCLUSIONS: The Spanish version of the MSTCQ questionnaire is a feasible, reliable and valid tool for the evaluation of satisfaction with the injection device in the treatment of MS.