Aim To synthesize clinical and scientific evidence regarding the instruments available to assess upper‐limb function in paediatric patients with neuromuscular disease (NMD). Method This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses and COnsensus‐based Standards for the selection of health Measurement INstruments (COSMIN) guidelines (Prospective Registry of Systematic Reviews no. CRD42020140343). Two independent reviewers searched the PubMed/MEDLINE, LILACS, Embase, and Scopus databases. Inclusion criteria were cross‐sectional or longitudinal studies or randomized controlled trials that used scales or questionnaires to assess upper‐limb function in paediatric patients with NMDs. The COSMIN Risk of Bias checklist and criteria for good measurement properties were applied to assess the methodological quality of the instruments. Results In total, 34 articles and 12 instruments were included. The Brooke Upper Extremity (n=16) and Performance of Upper Limb (PUL) (n=12) instruments were the most used tools. The PUL and Duchenne muscular dystrophy (DMD) Upper Limb patient‐reported outcome measures (PROMs) tested more measurement properties and provided higher methodological quality scores for patients with DMD. Likewise, the Revised Upper Limb Module (RULM) was the most suitable instrument for patients with spinal muscular atrophy. No instrument has been devised to assess upper‐limb function in patients with Charcot–Marie–Tooth disease and no other disease‐specific instruments were found. Interpretation The PUL, DMD Upper Limb PROM, and RULM are the most suitable instruments to assess upper‐limb function in the two most prevalent paediatric NMDs. The identified gaps and methodological flaws of the available instruments indicate a need to develop high‐quality instruments to assess other types of paediatric NMDs. The most suitable observer–rater instrument to assess upper‐limb function in Duchenne muscular dystrophy (DMD) is the Performance of Upper Limb. The most suitable observer–rater instrument to assess upper‐limb function in spinal muscular atrophy is the Revised Upper Limb Module. The DMD Upper Limb patient‐reported outcome measure is recommended to assess the upper‐limb performance of patients with DMD. Literature gaps and methodological flaws indicate the need to develop high‐quality instruments to assess other types of paediatric neuromuscular disease.