Seeds of flax or linseed (Linum usitatissimum L.) are important nutraceutical foods with antioxidant, anti-inflammatory, estrogenic, laxative, and antibacterial properties. Flaxseed oil and seeds are the richest vegetarian source of omega-3 fatty acids. Consumption of flaxseeds helps in prevention and control of cardiovascular disease, neurodegenerative disorders, obesity, diabetes mellitus, polycystic ovary syndrome, gout, liver and kidney dysfunction, oxidative stress-related diseases, post-menopausal symptoms, osteoporosis, irritable bowel syndrome, dry eye disease, cystic fibrosis, diarrhea, and cancer, particularly of the mammary and prostate gland cancer. Of late, flaxseed is gaining more importance not only because of its industrial values but also due to its nutraceutical and pharmaceutical properties. The literature review was performed using PubMed, Scopus, PubMed Central, Google Scholar, and Web of Science from 1995 onwards. Data was also obtained from websites/books/book chapters.