The objective was to determine the effects of low-dose, high-concentration, dual localized botulinum toxin A (BTX-A) injections on upper limb movement quality and function. Study design was an evaluator-blinded, randomized, controlled trial. Forty-two children (31 males, 11 females; range 2–8y, mean 4y [SD 1.6]) with hemiplegic cerebral palsy (Gross Motor Function Classification System level I) participated. All received occupational therapy. The treatment group (n=21) received one injection series (mean muscles injected 6 [SD 1.05]; total dose 82–220 units, mean 139 [SD 37.48]; dilution 100 units/0.5ml). Primary outcome of Quality of Upper Extremity Skills Test (QUEST) at 6 months was not significant (p=0.318). Secondary outcomes were average treatment effects at 1, 3, and 6 months, which favoured the treatment group: QUEST (p<0.001); Canadian Occupational Performance Measure (performance, p=0.002; satisfaction p=0.007); parent Goal Attainment Scaling (GAS; p=0.001), therapist GAS (p<0.001); Pediatric Evaluation of Disability Inventory (PEDI) functional skills (p=0.030); Ashworth (p<0.001). PEDI caregiver assistance was not significant (p=0.140). Therapy alone is effective, but at 1 and 3 months movement quality is better where BTX-A is also used. Moreover, function is better at 1, 3, and 6 months, suggesting BTX-A enhances therapy outcomes beyond the pharmacological effect. One- and 3-month Ashworth and QUEST scores suggest precise needle placement accuracy.