BACKGROUND Healthcare faces major challenges with provider safety and rising costs, and many organizations are using Lean to instigate change. One Lean tool, 5S, is becoming popular for improving efficiency of physical work environments, and it can also improve safety. OBJECTIVE This paper demonstrates that safety is an integral part of 5S by examining five specific 5S events in acute care facilities. We provide two arguments for how safety is linked to 5S:1. Safety is affected by 5S events, regardless of whether safety is a specific goal and 2. Safety can and should permeate all five S's as part of a comprehensive plan for system improvement. METHODS Reports of 5S events from five departments in one health system were used to evaluate how changes made at each step of the 5S impacted safety. RESULTS Safety was affected positively in each step of the 5S through initial safety goals and side effects of other changes. CONCLUSIONS The case studies show that 5S can be a mechanism for improving safety. Practitioners may reap additional safety benefits by incorporating safety into 5S events through a safety analysis before the 5S, safety goals and considerations during the 5S, and follow-up safety analysis.