This study conducted the analysis of changes in building construction project plan on project success during project execution in Akure Metropolis, Ondo state, Nigeria. The total sample size used for the study was 169, however 165 questionnaires were retrieved and analyzed. The data collected were analyzed using descriptive statistics, the Relative Importance Index (RII) and the hypothesis for the study were tested using Pearson Product moment correlation coefficients which revealed that changes in project plan have a statistical significant effect on project success, with r=-0.560, and p= 0.003. This results shows that there is a negative correlation between project success and effects of changes in project plan, which implies that as the effects of changes in project plan increases, which is caused by frequent changes in project plan, the success of the project tends to diminishes. From the findings of the research, the most important criteria for project success is the satisfaction of project stakeholders (RII= 0.965). The top effect of changes in project plan is increase in project cost (RII= 0.996). The study showed that having a knowledge–base of previous similar projects (RII= 0.989) is the most important way to mitigate changes in project plan. The study concludes that any alteration to the changes in project plan do have effects on the success of the project.