This special issue contains papers accepted by the ECML PKDD 2018 journal track for publication in Data Mining and Knowledge Discovery. The track originated in ECML PKDD 2013, with the aim of offering authors the opportunity to have a journal publication, while also being able to present their work in a conference setting. The journal track provides authors with the option to submit a paper to either Data Mining and Knowledge Discovery or Machine Learning that, if accepted, will appear in a special issue of the respective journal. Papers accepted to this year’s journal track will be presented by their authors at ECML PKDD 2018 in Dublin, Ireland, September 10–14, 2018. The goal of the journal track is to solicit high-quality, novel, and mature research that meets the standard of a journal paper, while still being amenable to a conference presentation. As such, survey papers and extensions of previously published conference papers were not eligible for submission. The ECML PKDD 2018 journal track was organized around five submission deadlines, distributed approximately evenly in five-week intervals between August 27, 2017 and January 28, 2018.