Introduction The aim of the study was to evaluate the intra- and inter-rater reliability, and validity of the Trunk Control Measurement Scale (TCMS) for tele-assessment in children with cerebral palsy (CP). Method A cross-sectional study was conducted with 36 children aged 4-18 years, diagnosed with hemiplegic CP. Participants underwent four TCMS assessments: in-person assessment, tele-assessment via videoconferencing, and two video-based tele-assessments scored by same rater and by a second rater. Reliability was analyzed using intraclass correlation coefficients (ICC). Discriminant validity was assessed by comparing TCMS tele-assessment scores between children with Gross Motor Function Classification System (GMFCS) levels I and II, while criterion validity was evaluated by examining the correlation between face-to-face and tele-assessment TCMS scores. Results Excellent reliability was observed between face-to-face and tele-assessment (ICC: 0.91; 95%CI: 0.83-0.95). TCMS tele-assessment also demonstrated excellent intra-rater reliability (ICC: 0.90, 95%CI: 0.80-0.94) and high inter-rater reliability (ICC: 0.82, 95%CI: 0.66-0.90). Criterion validity was confirmed by strong correlations between face-to-face and tele-assessment scores (r = 0.925, and r = 0.892, p < 0.001 for rater-1 and rater-2, respectively). The TCMS successfully discriminated children by functional levels, demonstrating discriminative validity (p = 0.002). Bland-Altman analysis revealed minimal systematic error, with internal consistency remaining high across all assessments (>0.88). Discussion TCMS is a valid and reliable tool for teleassessing trunk control in children with hemiplegic CP. These results may pave the way for developing child-specific, targeted telerehabilitation programs, bringing telerehabilitation closer to its primary aim of ensuring equal opportunities. This study was registered as a clinical trial (NCT06707831). https://clinicaltrials.gov/study/NCT06707831