This research presents release inventories of unintentionally generated dioxin-like polychlorinated biphenyls (dl-PCB) and hexachlorobenzene (HCB), which so far have not been developed or assessed. For the inventory development, the amended Toolkit methodology as developed for reporting under the Stockholm Convention on Persistent Organic Pollutants, has been applied. Based on the activity rate (AR) obtained from various statistical yearbooks, reports, or scientific literature, and the emission factors (EFs) suited to each technology level, we estimated the preliminary release inventories of unintentionally produced dl-PCB and HCB from 36 source categories in China for the reference year 2015. The result showed that in 2015, 656 g TEQ of unintentionally produced dl-PCB and 2,145,504 g (or 2146 kg) of unintentionally generated HCB were released in China from these 36 source categories. Most of dl-PCB and HCB was released to air, 71% or 60%, respectively. For comparison – and for the sources which could be estimated for all three unintentional POPs – the total releases of PCDD/PCDF were 5695 g TEQ per year. Of these, 78% were released to air. For dl-PCB and HCB, the vast majority of the releases from the source group 7 – Production and use of consumer goods - is found in the products and not in air. With respect to source attribution and releases to air, the source groups SG3 - Heat and power generation and SG2 - Ferrous and non-ferrous metal production dominate the air emission inventory. Due to the lack of EFs, the calculated releases to the water and land were not well covered, which overall results in an underestimation of the total releases for all unintentional POPs. For comparison, the release inventories from Japan and from several other countries that were developed using methodologies other than the UNEP Toolkit are presented as well. •Release inventories for dl-PCB and HCB as unintentional POPs in China developed.•‘Heat and power generation’ and ‘Ferrous/non-ferrous metal production’ dominate air emissions.•Within limits, releases of dl-PCB and HCB compare with PCDD/PCDF releases.•There are a few inventories from other countries for comparison.