The trend towards natural products in the world is increasing due to the increased drug resistance of infectious diseases, the high prices for drugs and the difficulty of access. Also, bacterial or viral diseases that are difficult to treat and need a long time for proper treatment cause important infections in people. Since effective drugs could not be developed for most viral infections, it is very important to find natural products against viruses to introduce them to the world of science. The antiviral activities of the aqueous and methanol extract from Ferula halophila Peşmen, an endemic species to Turkey, has been investigated against human respiratory syncytial virus (HRSV, ATCC-VR-26). The cytotoxic and antiviral properties of plant extracts were investigated in HRSV / HEp-2 cell systems, respectively by the colorimetric MTT assay. In the study, the titer of RSV was used as 100 TCID50 (50% tissue culture infective dose). While MNTC (Maximum non-toxic concentration) of methanol extract was 195.313 µg/mL and CC50 (50% cytotoxic concentration) was 4366.22 µg/mL, it was determined as MNTC = 390.625 µg/mL and CC50 = 4366.22 for aqueous extract. According to the results, methanol extract showed more toxicity than the aqueous extract. The MNTC of Ribavirin used as a positive control was determined as 0.98 µg/mL and CC50 was 110.40 µg/mL. As a result of the study, it was determined that the methanol extract was not effective, whereas the aqueous extract had a significant anti-HRSV activity with the values of 50.69 µg/mL EC50 (50% Effective Concentration) and 97.54 Selectivity Index (SI). The EC50 and SI values of Ribavirin were 2.39 µg/mL and 46.19, respectively. According to the results, we can explain the presence of antiviral activity only in the aqueous extract and the absence in the methanol extract by the high toxicity of it and the insolubility of the antiviral compounds in the methanol extract.