What Is Complexity?
Complexity is a characteristic of a program, project or its environment that is difficult to manage due to human behavior, system interactions, ambiguity and uncertainty. Complex situations have many interdependent parts whose combined behavior is hard to predict.
In Practice
Complexity arises from the number of connections, not just the number of parts: many stakeholders, tightly coupled systems, changing conditions and feedback loops. Teams cope by breaking work into smaller pieces, increasing transparency, shortening feedback cycles and adapting as they learn — rather than assuming a single plan will hold.
PMBOK 8 Context
Complexity is addressed in the Uncertainty performance domain of the PMBOK Guide, 8th Edition, and is a key reason tailoring matters. See also ambiguity and volatility.
FAQ
Complex vs. complicated? Complicated problems are hard but predictable with expertise; complex problems have emergent behavior that resists precise prediction.
How do you manage complexity? With adaptive, iterative approaches, strong communication and continual re-assessment.
Author: Tom, PMP-certified since 2004. Last updated: July 2026. Aligned with the PMBOK Guide, 8th Edition.