Arsenic and antimony has been determined by neutron activation analysis in a large number (109) of siliciclastic sedimentary rock samples from the western part of the Mecsek Mountains (Tisia Block), Hungary. Additionally, a total of 84 samples were selected for XRD mineralogy. The goal of this work is to determine the distribution and origin of the local natural background contents of these toxic elements. Concentrations of As and Sb in different Lower Permian to Lower Triassic lithostratigraphic units are higher than the normal global ranges represented by the Upper Continental Crust composition (1.5 and 0.2 mg/kg, respectively). In the studied mudrock samples, the median values for As and Sb range from 3.5 to 30.5 mg/kg, and from 1.1 to 2.0 mg/kg, respectively. In the sandstone samples, the median As contents range from 2.3 to 20.5 mg/kg, while the values for Sb range from 0.4 to 0.9 mg/kg. The highest metalloid contents were found in the Upper Permian Cserdi and Boda formations, which could be only of local importance as a source of As in the contamination process of soils and natural waters. The relatively enhanced metalloid content of these rocks could be related to hydrothermal activity in the region. Another possibility is that the source for background levels of As and Sb in these siliciclastic rocks could be the metalloid-bearing Fe oxides and oxyhydroxides coating mineral grains.