When children with significant communication difficulties experience pain, they are in dire need of an appropriate means to communicate their pain in order to receive appropriate treatment. Self-report – the first step in the hierarchy of pain assessment – may be problematic for these children. However, augmentative and alternative communication (AAC) can assist children with significant communication difficulties to communicate their pain. The main aim of this research study was to develop a list of pain-related vocabulary by using typically developing children, parents and teachers to suggest children’s vocabulary and then to socially validate the list by means of a stakeholder review. A sequential exploratory mixed methods design with four phases was employed: In Phase 1 (Qualitative phase), 50 children aged 4;0 to 12;11 years old participated in focus groups to discuss their experiences related to pain. The thematic analysis of the qualitative data in Phase 1, revealed themes that were used in Phase 2 to develop the instrument, a set of hypothetical physical pain scenarios (HPPS). The HPPS was also pilot-tested and adapted in Phase 2 (Measuring Instrument Development phase). In Phase 3 (Quantitative phase), a total of 74 children, 61 parents and 56 teachers participated to suggest vocabulary that children from two age groups (6;0–7;11 and 8;0–9;11 year-olds) would use to communicate their pain. Participants provided 629 pain-related words and/or phrases, that spread over in seven pain-related categories and 23 pain-related sub-categories. A composite list of 87 frequently occurring pain-related vocabulary items as used by children was compiled. In Phase 4 (Social Validation phase), the composite vocabulary list was socially validated by means of a stakeholder review by three literate adults who use AAC. Based on the results of the study, a model for the selection of vocabulary for sensitive topics is proposed.