Breastfeeding is immunoprotective and World Health Organization recommends exclusive breastfeeding for about six months with continuation of breastfeeding for one year or longer as mutually desired by mother and infant. But the target for duration of exclusive breastfeeding has not been reached in a significant number of women. It may be due to inflammatory breast disease such as milk stasis or lactational mastitis.In this chapter we discuss the most common complications of breastfeeding including milk stasis, mastitis, and breast abscess. Also idiopathic granulomatous mastitis, a less common condition, is discussed due to its confusing characteristics and not universally-accepted treatment strategies .Breastfeeding mastitis is inflammation of the breast that can be infectious or non-infectious. With proper diagnosis and treatment of this condition, more severe complications like breast abscess could be avoided, so that breastfeeding could be continued in some circumstances.