Introduction and objective: The study aims to assess the validity of the Timed Up and Go test in patients with type IV spinal muscular atrophy and to examine its correlation with the 6-Minute Walk Test and the Hammersmith Functional Motor Scale – Expanded (HFMSE) over an eight-month period. Materials and methods: Fourteen adult, ambulant patients with spinal muscular atrophy type IV were included in the study. All patients were treated with intrathecal injections of nusinersen and were on a maintenance dosing schedule – once every four months. Assessments were performed twice, eight months apart, however, this was to short observation period to conduct an evaluative analysis of the effectiveness of disease-modifying therapy in the treatment of spinal muscular atrophy as chronic neuromuscular disease. Results: HFMSE correlates negatively with the time required for the patient to complete the Timed Up and Go test. It also correlates positively with distance the patient is able to walk during the 6-Minute Walk Test. This demonstrates that all of these tools perform consistently in the assessment of spinal muscular atrophy patients. The Timed Up and Go test showed a moderate fall risk in four patients, and a high fall risk in one patient, which is significant for creating an individualised physiotherapy plan for each patient. Additionally, three patients were unable to perform the Timed Up and Go test again after eight months of treatment due to sustained injuries. In these cases, the test results indicated functional deterioration that was not captured by the other two assessments. Conclusions: The tests used in this study show consistent and complementary results. The Timed Up and Go test appears to be particularly sensitive for detecting functional decline in this patient group. This shows that the assessment tools used in the study have clinical utility and may be successfully used for planning rehabilitation and physiotherapeutic interventions tailored to each patient’s individual needs.