We present two-dimensional spectroscopic observations of the circumnuclear region of Mrk 509. The spectra show extended (off-nuclear) broad Balmer emission ( {FWZI}>1 5,000 km s-1) in a region of about 8" in diameter (8 kpc if H0=50 km s-1 Mpc-1). These features are interpreted as reflected radiation coming from the unresolved active nucleus. The nearly isotropic appearance of the scattering region can be explained within the framework of the unified picture for active galactic nuclei, if the scatterers lie outside the galaxy's disk; otherwise, the present observations would not support simple anisotropic models for the Seyfert nucleus in Mrk 509.