In this study, the effect of experience and learning in building construction projects was investigated using the log-linear model (straight line). For this purpose, a reputable construction company in Tehran was selected as the case study. The construction details of five building projects of this company, including two five-story buildings, one four-story building, and two fourteen-story buildings, were examined. In addition, project execution data in terms of schedule and cost were collected for all projects in four sections, including: 1) site preparation and foundation, 2) structural work, 3) finishing and completion, and 4) the entire project. Using the power model based on the cumulative learning of the projects under study, the learning rate values for the entire projects ranged from 82.75% to 92.69%, and a value of 89.10% was calculated for the final project. The results indicate that experience had a significant effect on the execution process of these five projects and led to a reduction in construction time per square meter-floor of the building, such that the average reduction in construction time for four projects was approximately 30%. Furthermore, regarding construction cost, the learning rate was calculated to be between 98.80% and 99.53%, indicating that changes in construction costs were influenced less by execution experience and were more likely affected by external factors such as fluctuations in material prices, labor wages, and economic conditions.