The integumentary system is the largest organ in the human body. It performs several functions, such as protecting the body from various injuries and hazards, controlling temperature, immunity, excretion, metabolism, sensation, and vitamin D production. Vitamin D is vital in maintaining bone health, muscle and nerve functions, immune and anti-inflammatory actions, etc. Bone health depends on calcium homeostasis, and vitamin D is critical for the absorption of the same. It also prevents osteoporosis. Skin (keratinocytes) initiates the biochemical process for synthesizing vitamin D. However, vitamin D has also been investigated in skin health and diseases. Current evidence indicates that vitamin D is essential for skin and hair health. For specific diseases like psoriasis and atopic dermatitis, there has been evidence for their positive correlation with serum vitamin D deficiency and evidence negating any such correlation. Nevertheless, oral vitamin D use in skin disease treatment and prevention is limited due to its multifactorial origin and the risk of other adverse effects. The present chapter briefly describes the relation and evidence of the integumentary system, skin health, and vitamin D.