Hydroprocessed renewable diesel (HRD-76) and synthesized isoparaffin (SIP-76) have been produced in sufficient quantity for testing by the US Navy, and demonstrated as compatible replacements or blend stock with marine diesel (NATO F-76). Operational limitations with respect to the lubricity, seal swell and cold-flow properties, however, need to be addressed before using 100% HRD-76 or SIP-76. Aromatics are known to improve seal swell and low-temperature characteristics. In this study, three commercial aromatic fluids (Aromatic 100, 150 and 200) produced from petroleum refining were added to HRD-76 and SIP-76 at various concentrations to investigate their impacts on the properties of the biofuel blend. The composition, hydrogen content and physicochemical properties of these aromatic fluids were determined according to ASTM methods and compared with that of biofuels and F-76. The seal-swell capability of the aromatic fluids and biofuel blends was investigated using nitrile O-rings, while the effects of aromatic fluids on fuel low-temperature quality were evaluated using differential scanning calorimetry. In addition, ASTM D5304 and D2274 tests were conducted to investigate the impacts of adding aromatics to biofuels on long-term storage and oxidative stabilities. Although the composition and characteristics of these three aromatics fluids varied, all were capable of inducing o-ring seal swell and adjusting the density of biofuels without significantly affecting the biofuels' stabilities. HRD-76 and aromatic fluid blends also exhibited liquid to solid phase transitions at lower temperatures and greater hydrophilicity than neat HRD-76.