Twenty-seven aqueous extracts obtained from 21 plants used in the treatment of respiratory tract infections as folk remedies in Turkey were investigated for their relative total phenolic contents and antioxidant, antibacterial, antimycobacterial, and antifungal activities. Antibacterial and antifungal activities against dermatophytes and yeast-like fungi were determined using the microdilution method. Antibacterial activity of all extracts was more pronounced against gram-positive bacteria than against gram-negative bacteria. These extracts also exhibited higher antifungal activity against Candida krusei than ketaconazole. Six extracts displayed antidermatophytic activity against Epidermophyton floccosum, while only 3 extracts were highly active against Trichophyton rubrum. The extracts showed strong activity against both Mycobacterium tuberculosis and Mycobacterium avium, except for the Teucrium polium, Urtica dioica, Salvia fruticosa, S. verticillata, Rosa canina (flower, shoot, and root), Rubus sanctus, and Crepis foetida extracts. Additionally, all extracts exhibited antioxidant activity in DPPH assay except for the Primula vulgaris, Ononis spinosa, Nepeta italica, Hedera helix, Lantana camara (orange flowers), U dioica, and C. foetida extracts. The highest total phenolic content was observed in R. canina root extract. No correlation was observed between biological activities and the amount of phenolic compounds. All plants used in this study could be potential sources of new antimicrobial agents.