This study proposes a method for observing the inside of a temporary structure covered with a construction safety net using an image processing technique and 3D modeling. Images of the temporary structures were obtained using unmanned aerial vehicles (UAVs). Observing the inside of temporary structures is limited to using UAVs due to construction safety nets that act as obstacles. To solve this problem, the histogram equalization and grayscale stretching techniques were used to visualize the inside of a temporary structure covered by safety nets. After verifying the proposed method with small scale specimens, the proposed method was applied to climbing formwork installed at a construction site. Three-dimensional modeling technique was combined with improved images that were processed using the proposed method. The results indicated that the proposed method could identify internal objects that were not visible owing to safety nets. By comparing the original and improved images obtained through applying the proposed method, four target objects located inside the climbing formwork that were not visible owing to safety nets were sufficiently identified in the improved images. Thus, the proposed method can be effectively applied to identify the internal objects of temporary structures covered with safety nets.