The conclusions of the European Food Safety Authority (EFSA) following the peer review of the initial risk assessments carried out by the competent authority of the rapporteur Member State The Netherlands for the pesticide active substance (3E)-3-decen-2-one and the considerations regarding the proposal for inclusion of the active substance in Annex IV of Regulation (EC) No 396/2005, are reported. The context of the peer review was that required by Regulation (EC) No 1107/2009 of the European Parliament and of the Council. The conclusions were reached on the basis of the evaluation of the representative use of (3E)-3-decen-2-one as a plant growth regulator on potatoes. The reliable endpoints concluded as being appropriate for use in regulatory risk assessment, derived from the available studies and literature in the dossier peer reviewed, are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.