Information on persistent organic pollutants, and other pollutants (trace metals, inorganic, biological contaminants), remains scarce in Ethiopia with a limited number of studies that have been carried out in the past. Hence, during this study we analyzed PCDD/F and dl-PCB activities in sludge and sediment samples collected from wastewater treatment plant, industries, and rivers found in the city of Addis Ababa by means of the CALUX bioassay. The BEQ values detected in samples from WWTP ranged between 1.7 and 9.8 pg BEQ /g for PCDD/Fs and between 1.3 and 3.3 BEQ pg/g for dl-PCBs. PCDD/F activities from industrial sludge ranged from 0.90 to 3.1 BEQ pg/g, while the PCB levels ranged between 0.53 and 5.4 BEQ pg/g. The average levels of PCDD/F and dl-PCBs in sediment samples were 14.7 and 0.89 BEQ pg/g, respectively. The study showed both industrial and domestic wastes as potential sources for PCDD/Fs and dl-PCBs in the city. Even though lower levels of PCDD/Fs and dl-PCBs were detected, large variations due to sampling heterogenity made it difficult to rule out any potential adverse impacts. However, as a first screening of this kind for the city, the results are highly significant and suggest to launch further in-depth investigations.