Background <p>Children with cerebral palsy have weak muscle strength which affects range of available motion and reflects on distal dexterity. These may have an impact on their mobility and efficiency of daily living activities. Vibration has been regarded as an effective exercise method to improve muscle strength and endurance.</p> Objective <p>This study aimed to determine the effect of adding whole-body vibration to sling exercise therapy on shoulder muscle strength in children with cerebral palsy.</p> Materials and methods <p>A randomized controlled trial was conducted at the outpatient clinic of the Faculty of Physical Therapy at Cairo University. Fifty children with cerebral palsy aged 4–9 years (mean age 6.33 ± 2.09 years; 29 males, 21 females) participated. They were randomly divided into two equal groups. The control group (<i>n</i> = 25; 14 males, 11 females; mean age 6.28 ± 2.07 years) received conventional physical therapy plus sling exercise therapy. The study group (<i>n</i> = 25; 15 males, 10 females; mean age 6.38 ± 2.12 years) received the same conventional therapy and sling exercise therapy with added whole-body vibration. Shoulder muscle strength was assessed using the Lafayette manual muscle tester before and after 12 weeks of treatment. Mean differences, 95% CIs, and p-values were calculated.</p> Results <p>The study group demonstrated significantly greater improvement in muscle strength across all tested movements compared to the control group. For right shoulder flexors, the mean difference between groups was 2.73&#xa0;kg (95% CI: 1.94 to 3.52, <i>P</i> = 0.0001). Left shoulder flexors showed a mean difference of 2.83&#xa0;kg (95% CI: 2.01 to 3.65, <i>P</i> = 0.0001). Right shoulder abductors demonstrated a mean difference of 2.50&#xa0;kg (95% CI: 1.58 to 3.42, <i>P</i> = 0.0001). Left shoulder abductors showed a mean difference of 2.56&#xa0;kg (95% CI: 1.56 to 3.56, <i>P</i> = 0.0001).</p> Conclusion <p>Adding whole-body vibration to a regular physical therapy program significantly improves shoulder muscle strength in children with cerebral palsy. This intervention can be a valuable adjunct to enhance upper limb strength in these children.</p> Trial registration <p>The trial was registered at Clinical Trial.gov and the registration number was NCT07096089. Registered 29 July 2025 - Retrospectively registered, <a href="https://register.clinicaltrials.gov/prs/beta/studies/S000DZH100000042/recordSummary">https://register.clinicaltrials.gov/prs/beta/studies/S000DZH100000042/recordSummary</a>.</p>