Pain is common for children with intellectual and developmental disabilities (I/DD), yet specialized caregiver-based education is lacking. Objectives: This parallel group RCT tested effectiveness of the Let’s Talk About Pain training on respite workers’ (RW) pain-related knowledge and feasibility-confidence-skill ratings using between-group (pain vs. control) and within-group (pain training only) analyses. Methods: Fourteen children’s respite organizations were randomized using sequentially numbered, opaque, sealed envelopes to receive pain or control training. Researchers were blind until randomization; allocations were not explicitly revealed to organizations and participants. Participants (nintervention = 66; ncontrol = 92) underwent a 3-3.5 hour training and completed pain-related knowledge measures and feasibility-confidence-skill ratings at pre, post and 4-6 week follow-up. Intention-to-treat (nintervention = 65; ncontrol = 92) and per-protocol (nintervention = 26-38, ncontrol = 40-57) analyses were conducted. Results: Participants receiving pain training demonstrated (a) significantly higher pain knowledge and feasibility-confidence-skill ratings at post and follow-up versus control group and (b) significant increases in knowledge from pre-post. Despite a small decrease in mean scores, significant gains in knowledge and confidence-skill ratings were maintained from post-follow-up. Discussion: Results demonstrated improvements in RW knowledge and feasibility-confidence-skill ratings. This represents a promising step towards enhancing pain-related care provided to children with I/DD.