Difficulty in managing oral secretions is commonly experienced by patients with amyotrophic lateral sclerosis (ALS)/motor neurone disease (MND) and associated bulbar weakness including dysphagia. There are no definitive evidence-based treatment guidelines to manage the distressing symptom of drooling. We reviewed the evidence for the effectiveness of botulinum toxin injections to reduce saliva in ALS/MND. The search strategy was conducted in four stages: (1) electronic search of relevant databases, (2) hand searches of all international ALS/MND symposium journals, (3) email request to MND care centres in the UK and Ireland, and (4) hand searching of reference lists. All studies were critically appraised and relevant data extracted. Botulinum toxin type A and type B were analysed separately. Due to heterogeneity, it was not possible to calculate a pooled estimate of effect. Twelve studies met the inclusion criteria (9 for type A and 3 for type B). Only two randomised controlled trials were identified. Study sample sizes were small with a mean of 12.5 subjects. The most frequently reported outcomes were weight of cotton rolls and number of tissues used. All studies claimed the intervention tested was effective, but only seven studies (4 for type A and 3 for type B) reported statistically significant differences. Although there is evidence to suggest that botulinum toxin B can reduce drooling, the evidence base is limited by a lack of randomized controlled trials. Evidence to support the use of botulinum toxin A is weaker. Larger trials will help remove the uncertainty practitioners face in treating this disabling symptom.