The construction of buildings with cross-laminated timber (CLT) panels has grown steadily in recent years, mainly because of the environmental advantages of wood over other building materials. However, there are still doubts about the dynamic behavior of CLT buildings in countries with high seismicity and how their dynamic properties vary with temperature and relative humidity changes. The present work shows the modal properties’ monitoring of a 5-story CLT building prototype. The prototype building is located in Chile and has dimensions of 4.04 m, 6.44 m, and 14.5 m for width, length, and height, respectively. The CLT panels are made of radiata pine wood, and the joints between panels were executed with self-drilling screws and metal hardware (hold-down and angle-bracket). The CLT building was instrumented with ten uniaxial accelerometers (model PCB393B12) distributed on different floors and directions to measure the lateral dynamic response to environmental vibrations. The five main frequencies, damping ratios, and modal shapes were estimated through the operational modal analysis methods EFDD and SSI. Preliminary results suggest that, on average, the lateral and torsional frequencies measured in the CLT building were between 3.13 Hz and 13.88 Hz. These experimental results will allow a process of calibration and updating of finite element models of this type of buildings for their subsequent incorporation into Chilean structural design regulations.