This study determined the bioactive composition and antioxidant potential of parsley, chives and their mixture (Brazilian cheiro-verde). Additionally, the effect of these herbs against cholesterol oxidation in grilled sardines (Sardinella brasiliensis) was also investigated. Ultra-high Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (UHPLC-ESI-MS) analyses revealed the presence of phenolic acids (caffeic, chlorogenic, and ferulic acids) and flavonoids (apigenin, kaempferol, catechin) in the herbs. Higher levels of phenolics (2.10 ± 0.02 mg GAE/g) and carotenoids (205.95 ± 0.17 µg/g) were determined in parsley extracts. Moreover, parsley also presented higher antioxidant capacity by DPPH (59.21 ± 0.07 %) and ORAC (109.94 ± 18.7 µM TE/g) than the other herbs. In vivo analyses demonstrated that the herbs’ extracts decreased the damage on Saccharomyces cerevisiae cells exposed to H2O2, except the chives extract at 10 μg/mL. Higher levels of cholesterol oxidation products (COPs) were determined after grilling. The total COPs increased from 61.8 ± 0.7 (raw fish) to 139.7 ± 10.1 µg/g (control). However, the addition of herbs effectively reduced cholesterol oxides formation, this effect was more pronounced in fish containing 4% parsley and 4% cheiro-verde. Promising results were found for cheiro-verde; however, it did not present synergic antioxidant effects.