Background: Children born with a cleft palate with or without cleft lip (CP ± L) are known to be at risk for speech-language disorders that impact educational and social-emotional growth. It is hypothesized that speech-language intervention delivered before the age of 3 years could decrease the impact of CP ± L on speech-language development. Infant sign training in combination with verbal input expands the natural communication of young children including multimodal speech-language input (i.e., verbal and manual input) via caregivers who act as co-therapists. Aims: To determine the effectiveness of infant sign training in 1-year-old children with CP ± L by comparing different interventions. Methods & Procedures: This is a two-centre, randomized, parallel-group, longitudinal, controlled trial. Children are randomized to either an infant sign training group (IST group), a verbal training group (VT group) or no intervention control group (C group). Caregivers of children who are assigned to the IST group or VT group will participate in three caregiver training meetings to practise knowledge and skills to stimulate speech-language development. Outcome measures include a combination of questionnaires, language tests and observational analyses of communicative acts. Outcomes & Results: It is hypothesized that speech-language development of children with CP ± L will benefit more from IST compared with VT and no intervention. Additionally, the number and quality of communicative acts of both children and caregivers are expected to be higher after IST. Conclusions & Implications: This project will contribute to the development of evidence-based clinical practice guidelines regarding early speech-language intervention in children with CP ± L under the age of 3 years.