Understanding the sources of complexity in advanced Nuclear Power Plant (NPP) control rooms and their effects on human reliability is critical for ensuring safe performance of both operators and the entire system. New generation control rooms will rely more heavily on automation and computerized Human-System Interfaces (HSI). Without proper management, information representation and required operator-system interaction could challenge operator information processing capabilities. This paper provides an initial step in assessing the sources of complexity in the NPP control rooms and introduces a systems-theoretic descriptive model of these sources of complexity leveraging network theory. Copyright 2010 by Human Factors and Ergonomics Society, Inc. All rights reserved.