Fungicides are widely used in agriculture to control fungal diseases. After application, fungicides can be transported offsite to surface and ground water and ultimately enter estuarine/marine environments. The presence of fungicides in the marine environment may pose risks to marine organisms but little is known about fungicide effects on these organisms, especially invertebrates. The present study investigated the effects of the commonly used boscalid fungicide Filan® on life history traits, feeding rate and energy reserves (lipid, glycogen, and protein content) of the marine amphipod Allorchestes compressa over six weeks under laboratory conditions. Amphipods were exposed to three concentrations of Filan® (1, 10, and 40 µg a.i./L) with five replicates per treatment. Lipid content and reproduction were the most sensitive measures of effect with lipid content reduced by 53.8% at the highest concentration. Survival, growth, and other energy reserves of amphipods were also negatively affected by Filan(®) and the effects were concentration dependent. Antennal deformities were incidentally observed on the amphipods at concentration of 40 µg a.i./L. The results of this study indicate comprehensive effects of boscalid fungicide Filan® on A. compressa at environmentally relevant concentrations. The decline or absence of A. compressa in marine ecosystems could impair the ecosystem function because of their important role in the trophic transfer and nutrient recycling. Our results suggest that even though the use of fungicides is often regarded as posing only a minor risk to aquatic organisms, the assessment of their long term effects is critical. This article is protected by copyright. All rights reserved.