The sequencing of the Crassostrea virginica genome has brought back the interest for gene delivery and editing methodologies. Here, we report the expression in oyster hemocytes of two heterologous expression vectors under the CMV promoter delivered with dendrimers. Expression was monitored using confocal microscopy, flow cytometry, and immunofluorescence assay. C. virginica hemocytes were able to express the green fluorescence protein and Crassostrea gigas vascular endothelial growth factor under CMV viral promoter both in vivo and in vitro. These results provide the bases for interrogating the genome and adapting genome editing methodologies. Image 1 • Crassostrea virginica hemocytes can be transfected in vivo and in vitro. • Heterologous expression vector under viral control works with C. virginica hemocytes. • Plasmids delivered using dendrimers. • Transfection efficiency is low. [ABSTRACT FROM AUTHOR]