Abstract Cross-laminated timber (CLT) is increasingly used as shear walls in timber structures due to its excellent structural properties, fire resistance, dimension stability, carbon sequestration capabilities, and energy efficiency, but the effectiveness of this material for airborne sound insulation has received little attention. Here, airborne sound insulation was tested for nine full-scale CLT walls. The impacts of half-lap joints, CLT thickness, and CLT composite wall with gypsum board (GB) and light frame cladding were determined. Single number indexes and weighted sound reduction index (Rw) values were calculated. The results revealed that half-lap joints had no impact on sound insulation of CLT bare wall. The 175 mm thick CLT and 105 mm thick CLT bare wall sheathed with GB and light wood frame exhibited slightly better airborne sound insulation than the 105 thick CLT bare wall, with an increase in Rw from 32 to 38 dB and change in sound insulation class from 3 to 4, but these materials do not meet the requirement for internal separation components in residential buildings. The CLT composite walls sheathed with stagger studs, light steel frame, damping coating, and deadening felt achieved Rw values ≥42 dB, leading to increases in airborne sound insulation class to levels 5 and 6. A simplified statistical energy analysis model was developed for the CLT composite wall system with a light frame and the predicted Rw values matched well with the experimental results.