The aim of this article is to review postpartum fatigue, especially as it relates to the occurrence and pathophysiology of three common postpartum conditions known to contribute to fatigue: anemia, infection/inflammation, and thyroid dysfunction. Fatigue is an unrelenting condition that affects physical and mental health, and it has implications for everyday activities, motivation, and social interactions. Although individuals of all ages and both genders are at risk for developing fatigue, postpartum fatigue is particularly challenging, because the new mother has demanding life tasks to accomplish during this period of time. Postpartum fatigue may impact postpartum maternal role attainment and may place a woman at increased risk for postpartum depression. Although several treatable physiological conditions common during the postpartum period are known to increase fatigue, none of these conditions is a part of the usual assessment of healthy postpartum women. For many women, subtle fatigue may develop, linger or worsen, and even lead to depression, with both the woman and her care provider unaware.