In this letter we present clear evidence that Mrk 573 is an obscured Narrow-Line Seyfert 1 (NLSy1) and not an archetypal Seyfert 2, as it has been classified until now. Only three galaxies have been proposed as members of this class, prior to this work. Here we report near-infrared spectroscopic data taken with LIRIS on the 4.2 m William Herschel Telescope (WHT). Our high quality near-infrared nuclear spectrum in the 0.88-1.35 micron wavelength range shows the permitted O I 1.128,1.317 micron narrow lines, the Fe II 9200-Å lines and the Fe II 1-micron lines, together with a relatively broad component (~1700 km/s) of Paschen Beta. These features can originate only in an optically thick high density region, similar to those observed in the Broad Line Region (BLR). Comment: 12 pages, 4 figures, accepted for publication in ApJ Letters