Several complications attributed with Herpes virus related infections and the emergence of drug resistant viruses prompt scientists to search for new drugs. Several terpenoids and coumarins have shown anti HSV effects while no sesquiterpene coumarins have been previously tested for HSV treatment. Three sesquiterpene coumarins badrakemin acetate (1), kellerin (2) and samarcandin diastereomer (3) were isolated from the gum resin of Ferula assa-foetida, a herbal medicine with antimicrobial, antiprotozoal and antiviral effects. Compounds were identified by 1D and 2D- NMR spectroscopies and comparison with literature data. A comparative evaluation of cytotoxicity and antiviral activity showed that kellerin (2) could significantly inhibit the cytopathic effects and reduce the viral titre of the herpes virus type 1 (HSV-1) DNA viral strain KOS at concentrations of 10, 5 and 2.5 µg/mL.