The purpose of this study was to validate complex- and magnitude-based quantitative chemical-shift encoded MRI (CSE-MRI) to quantify PDFF as an accurate biomarker of hepatic steatosis. A biopsy-MRI correlation study was performed in 95 obese subjects undergoing bariatric weight loss surgery. The results of biochemical triglyceride, conventional histological, digital histological, and MR spectroscopy analyses were used as reference standards. Strong correlations were found between MRI-PDFF measured using both complex- and magnitude-based CSE-MRI methods vs. each reference standard. This is the first cross-sectional in-vivo study validating PDFF as a biomarker of hepatic steatosis using biochemical triglyceride concentration as the reference.