Cross laminated timber (CLT) is a relatively new engineered wood product that has elevated the prospects of utilizing wood as the primary structural material for mid and high rise buildings. The hygrothermal performance of CLT, however, is still not well understood at the material, assembly and building scales. A major concern lies in exposure to heavy moisture loads during construction that can result in moisture build up after assembly and enclosure, and localized damage (e.g., delamination). The objectives of this research were to better understand the hygrothermal performance of Douglas-fir CLT at multiple scales, to develop and define moisture sampling criteria and monitoring protocols, and to distill practicable moisture management insights for industry. In order to achieve these objectives, a multiscale moisture monitoring campaign was devised that began at the material/laboratory scale with cyclic weathering tests and ended with moisture monitoring of a mass timber structure during the early phases of construction. Results at the laboratory scale showed that while CLT was generally resilient to short duration wetting events, it was also prone to slow drying and moisture pooling/ingress at the gaps and wane on the upper plies. CLT also showed high levels of checking and other damage at exposed edges. The Forest Science Complex, which was monitored during construction, showed good hygrothermal performance when compared to other monitoring precedents, but showed high moisture levels at distinct areas.