This paper presents an analysis of access mode choice by riders of one of the first U.S. suburb-to-suburb commuter railroads, the Westside Express (WES), in the Portland, Oregon metropolitan area. The study uses on-board survey data collected by the region’s transit agency, Tri-Met, during WES’s first year of operation. The data include observed access mode choices, historical mode usage, and subjective assessment of WES attributes. A hierarchical choice model was estimated, using attributes of the access trip, station areas and rider characteristics. The estimation results revealed pre-WES-mode inertia effects in choosing drive access, pro-sustainability attitudes in choosing bike access, the importance of comfort to light rail and auto users, and strongly positive station-area effects of feeder bus lines and parking provision. The hierarchical choice model revealed significant substitution effects between drive and light rail modes and between bike and walk modes. This study provides potentially valuable insights to agencies for the purposes of station-area planning and targeted marketing efforts.