Flax (Linum usitatissimum L.) is an important oil seed crop that is mostly cultivated in temperate climates. In addition to many commercial applications, flax is also used as a fibrous species or for livestock feed (animal fodder). For the last 40 years, flax has been used as a phytoremediation tool for the remediation of different heavy metals, particularly for phytoextraction when cultivated on metal contaminated soils. Among different fibrous crops (hemp, jute, ramie, and kenaf), flax represents the most economically important species and the majority of studies on metal contaminated soil for the phytoextraction of heavy metals have been conducted using flax. Therefore, a comprehensive review is needed for a better understanding of the phytoremediation potential of flax when grown in metal contaminated soil. This review describes the existing studies related to the phytoremediation potential of flax in different mediums such as soil and water. After phytoremediation, flax has the potential to be used for additional purposes such as linseed oil, fiber, and important livestock feed. This review also describes the phytoremediation potential of flax when grown in metal contaminated soil. Furthermore, techniques and methods to increase plant growth and biomass are also discussed in this work. However, future research is needed for a better understanding of the physiology, biochemistry, anatomy, and molecular biology of flax for increasing its pollutant removal efficiency.