Thisbook constitutes the thoroughly refereed post conference proceedings of thesecond edition of the Semantic Web Evaluation Challenge, Sem Web Eval 2015, co-located with the 12th European Semantic Web conference, held in Portoroz, Slovenia, in May/June 2015.This book includes thedescriptions of all methods and tools that competed at Sem Web Eval 2015, together with a detailed description of the tasks, evaluation procedures anddatasets. The contributions are grouped in the areas: open knowledge extractionchallenge (OKE 2015); semantic publishing challenge (Sem Pub 2015);schema-agnostic queries over large-schema databases challenge (SAQ 2015);concept-level sentiment analysis challenge (CLSA 2015).