Lippia graveolens is one of the most important aromatic species in Mexico due to antioxidant and antibiotic activities reported in its essential oil. The aim of this work was to assess the effect of irrigation with aquaculture wastewater and salicylic acid addition on the production of phenolic compounds in L. graveolens. L. graveolens plants (14) were irrigated with aquaculture wastewater and (14) using Steiner solution for 28 days; at the same time, salicylic acid was exogenously applied at 0.0 (control), 0.5 and 1.0 mM concentrations in both treatments at 5 and 19 experimental days. The total phenolic content was measured by Folin–Ciocalteu, the flavonoid content was determined by the aluminum chloride method, and the antioxidant capacity was measured by DPPH and FRAP assays. The results showed an increase in the total phenolic and flavonoid content in plants irrigated with aquaculture wastewater solution (17.25 ± 2.35 to 38.16 ± 4.47 mg eq GA·g⁻¹ W). The antioxidant capacity was higher in plants irrigated with Steiner solution (98.52 mg eq T·g⁻¹ W). In conclusion, L. graveolens irrigated with aquaculture wastewater leads to an increase in the total phenolic content and Steiner-solution antioxidant capacity in plants.