OBJECTIVES: This study examines the impact of Lean “inflow” change on patient satisfaction at a primary care pilot clinic location of a large, multispecialty healthcare provider in Northern California undergoing system-wide transformation. METHODS: The healthcare provider serving 2+ million patients has invested a significant amount of resources in Lean management to transform the way primary care is delivered.  The Press Ganey (PG) outpatient survey was used. The monthly PG score, covering a two-year period, compared pre and post-implementation of Lean in the pilot site relative to two comparison sites. Monthly site differences between pilot and comparators in median PG scores were calculated as the dependent variable. Segmented regression with a breakpoint at the start of the intervention was used to analyze departmental PG scores over time, adjusting for clinical FTE and autocorrelation.  RESULTS: Relative to comparator 1, there was a significant trend post Lean implementation of 0.2 percentage point per month (p=0.002) in pilot site Internal Medicine and 0.1 percentage point per month (p=0.004) in pilot site Pediatrics. There were significant trends post Lean implementation of 0.5 percentage point per month (p<0.001) in pilot site Family Medicine and Pediatrics relative to comparator 2. Besides, there was an immediate and 2 percentage points (p<0.001) increase in pilot site relative to comparator 2 at the intervention month. CONCLUSIONS: Lean “inflow” changes had improved patient satisfaction in pilot site Pediatrics by 1.9 and 7.5 percentage points relative to two comparators, respectively. Patient satisfaction in pilot site was estimated to increase by 2.7 percentage points relative to comparator 1 for Internal Medicine and 7.6 percentage points relative to comparator 2 for Family Medicine after Lean was implemented, based on the trend of site differences in the preceding year. Overall, Lean “inflow” change seemed to improve primary care patient satisfaction.