Minocycline and doxycycline both are second-generation tetracycline antibiotics with similar chemical structures and comparable antibacterial spectrum. Minocycline has also emerged as the tetracycline of choice for multidrug-resistant Acinetobacter baumannii infections, although doxycycline has also shown the activity. Minocycline showed promising results in experimental neurology, which was due to its highly lipophilic nature. It is clinically safe and effective adjunct to antipsychotic medications. The objective of the current review is to provide clinical and preclinical, non-antibiotic uses of minocycline as well as doxycycline. Relevant literature covers antibiotic actions but is more specifically concerned with the non-antibiotic biological aspect of tetracyclines. Non-antibiotic biological effects for both the antibiotics were identified through searching relevant databases including: PubMed, Scopus, and Web of Science up to 2020, using the keywords 'minocycline and doxycycline'. Anti-inflammatory, anti-oxidant, anti-apoptotic neuroprotective, immunomodulatory and the number of other non-antibiotic effects were compiled for minocycline and doxycycline.