Eric Nielsen's research focuses on the direct detection and characterization of extrasolar planets, including key roles in the VLT/MMT Simultaneous Differential Imaging Survey, the Gemini NICI Planet-Finding Campaign, and the Gemini Planet Imager Exoplanet Survey. Specific research topics include determining the underlying distribution of planets, determining the ages of stars, astrometric confirmation of planet candidates, and orbital determination of substellar companions.