Multiple sclerosis (MS) is a demyelinating central nervous system disease that leads to neurological disability. Brain-derived neurotrophic factors (BDNFs) are neurotrophins involved in neurodegenerative disorders. This study analysed the relationship between serum BDNF, neurological disability and different MS treatments. We included 63 people with MS (PwMS), with relapsing-remitting MS or clinically isolated syndrome, and 16 healthy controls (HCs). We analysed the serum levels of BDNF and MS specific disability tests (Expanded Disability Status Scale, timed 25-foot walk test, nine-hole peg test), at baseline (V0) and after one year of interferon beta1a or teriflunomide treatment (V1). Baseline BDNF values were not different between the PwMS and HCs (p = 0.85). The BDNF levels were higher in PwMS vs. HCs after treatment (p = 0.003). BDNF was not related to last-year relapses or by the disease duration (all p > 0.05). The overall values for the PwMS decreased after one year (p < 0.001). Both treatments implied a similar reduction. BDNF was not related to neurological disability (p > 0.05). BDNF values were not influenced by the lesion burden, active lesions, or new lesions on MRI (p > 0.05). In our cohort, the PwMS had higher BDNF levels compared to the HCs after one year of treatment. BDNF was not related to clinical or paraclinical disease severity signs.