This study evaluated the total phenolic content and antioxidant capacity of 70 medicinal plant infusions using the Folin–Ciocalteu assay and the Ferric Reducing/Antioxidant Power (FRAP) assay, respectively. The phenolic content ranged from 9 to 2218 mg/L, and the FRAP values ranged from 0.06 to 25 mM/L, showing a significant linear correlation between the two measures. The infusions were categorized into five groups based on their FRAP values: very low (<1 mM/L), low (1–5 mM/L), good (5–10 mM/L), high (10–20 mM/L), and very high (>20 mM/L). The Phenol Antioxidant Coefficient (PAC) was calculated for each infusion, ranging from 1.1 to 3.9. *Melissa officinalis* infusions showed the highest antioxidant capacity, with high phenolic content, very high FRAP (>20 mM/L), and PAC > 3. The study also investigated the effects of infusion time and temperature on phenolic content and antioxidant capacity, finding that higher temperatures and longer infusion times increased antioxidant activity. Additionally, *Melissa officinalis* infusions demonstrated strong scavenging abilities against the DPPH and ABTS radicals, comparable to or better than those of vitamin C and Trolox. These findings suggest that *Melissa officinalis* infusions could be a significant dietary source of potent antioxidants.This study evaluated the total phenolic content and antioxidant capacity of 70 medicinal plant infusions using the Folin–Ciocalteu assay and the Ferric Reducing/Antioxidant Power (FRAP) assay, respectively. The phenolic content ranged from 9 to 2218 mg/L, and the FRAP values ranged from 0.06 to 25 mM/L, showing a significant linear correlation between the two measures. The infusions were categorized into five groups based on their FRAP values: very low (<1 mM/L), low (1–5 mM/L), good (5–10 mM/L), high (10–20 mM/L), and very high (>20 mM/L). The Phenol Antioxidant Coefficient (PAC) was calculated for each infusion, ranging from 1.1 to 3.9. *Melissa officinalis* infusions showed the highest antioxidant capacity, with high phenolic content, very high FRAP (>20 mM/L), and PAC > 3. The study also investigated the effects of infusion time and temperature on phenolic content and antioxidant capacity, finding that higher temperatures and longer infusion times increased antioxidant activity. Additionally, *Melissa officinalis* infusions demonstrated strong scavenging abilities against the DPPH and ABTS radicals, comparable to or better than those of vitamin C and Trolox. These findings suggest that *Melissa officinalis* infusions could be a significant dietary source of potent antioxidants.