This paper introduces a method to capture labor performance loss due to project scope changes. It addresses the impact of scope change on the direct labor performance during the construction phase of projects. Generally, such indirect effect of changes is difficult to capture when estimating the cost of the added scope and poses challenges to the project management team in convincing project owners of the legitimacy of such added cost. Therefore, contractors end up absorbing this cost or filing claims to recover financial losses. The procedures for calculating the performance factor loss due to changes involves integrating baseline schedule, earned value management system, measured mile analysis, and project actual data. The developed method was applied to a construction project in northern Alberta. The site data pertinent to electrical trades was collected over a period of nine months to calculate the difference between labor performance indices of original scope and changes. The calculations were performed cumulatively to account for the ripple effect of the introduced scope changes. Analysis of the results generated reveals a negative correlation between the intensity of changes and labor performance. Changes that are not properly documented and managed can severely affect the project schedule and its total cost. Therefore, the authors recommend proactive management procedure to limit the adverse primary and secondary effects of project scope changes.