AbstractFollowing a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on an ethanolic extract of the dried biomass of the microalgaPhaeodactylum tricornutumas a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF is an ethanolic extract of the dried biomass of the microalgaP. tricornutumdiluted in a medium‐chain triglyceride oil carrier, with standardised fucoxanthin and tocopherol content. The main component of the NF is fat (78% on average), followed by crude protein (10% on average). The Panel is of the view that a consistent and safe production process has not been demonstrated. Additionally, the Panel considers that the information provided on the composition of the NF is not complete and may raise safety concerns. The applicant proposed to use the NF as a food supplement at the use level of 437 mg/day, with the target population being adults, excluding pregnant and breastfeeding women. There is no history of use of the NF or of its source, i.e.P. tricornutum. The Panel notes that the source of the NF,P. tricornutum, was not granted the qualified presumption of safety (QPS) status by the EFSA Panel on Biological Hazards (BIOHAZ), due to the lack of a safe history of use in the food chain and on its potential for production of bioactive compounds with toxic effects. There were no concerns regarding genotoxicity of the NF. In the 90‐day study provided, a number of adverse effects were observed, some of them seen already at the lowest dose tested (750 mg/kg body weight (bw) day), which was identified by the Panel as the lowest‐observed‐adverse‐effect‐level (LOAEL). The potential phototoxicity of pheophorbide A and pyropheophorbide A in the NF was not addressed in this study. Although noting the uncertainties identified by the Panel regarding the analytical determination of these substances in the NF and the limitations in the publicly available toxicity data, a low margin of exposure (MoE) was calculated for these substances at the proposed use levels. The Panel concludes that the safety of the NF under the proposed uses and use levels has not been established.