This dataset presents abundance data of juveniles Mugil liza recorded in surf-zone in south Brazilian coast. The fish were collected monthly between June 2011 and May 2012 in the surf zones adjacent to the mouths of the six estuaries from 29°S, 48°W to 34°S, 53°W. Two marine surf zone sampling points were selected at each site. At each sampling point, we collected five samples monthly. Each beach seine sample was conducted perpendicular to the beach at a depth of 1.5 m. The beach seine net was 9 m long and 1.5 m high with 13 mm knot-to-knot mesh in the wings and 5 mm knot-to-knot mesh in the 3 m central section. Each haul covered an area of approximately 120 m2. Mullet abundance data is the total number of individuals per sampling event. Water temperature (°C) and salinity were recorded monthly at each sampling event using a digital multiparameter probe. The salinity was measured using the Practical Salinity Scale (PSU). The water transparency was measured using a Secchi disk (cm). This study was conducted in accordance with the recommendations of the Brazilian Ministry of the Environment (MMA), and all data collection and fish handling were endorsed by the Permanent License for Collection of Zoological Material. The dataset were formatted according to the Darwin Core (DwC) standard (TDWG 2015).