The farm of Cairo Aromatic located in Farafra Oases (New Valley) was subjected to a field experiment through two successive seasons (2022 and 2023) to evaluate the effect of potassium sulfate K₂SO₄ (0.0, 90, 180 and 270 kg/fed) on oil production (volatile oil %, volatile oil yield either per m² per cut or per fed per cut and total volatile oil yield per season) and some chemical constituents of spearmint and peppermint. Data showed that all previous traits were significantly augmented with Mentha spicata than Mentha piperita in all cases, except oil percentage, the superiority was for Mentha piperita. Also, such abovementioned parameters were increased with increasing potassium fertilization level, where 270 kg/fed of K₂SO₄ produced the highest values in all cases. Also, potassium fertilizer increased pigments (chlorophyll contents) and N, P and K%. The interaction was significant for all studied parameters in all cases. Interestingly, the combination treatment between the high level of potassium with Mentha piperita was the best in essential oil percent, while the highest yield of essential oil due to high level of potassium with Mentha spicata.