Insomnia is a common disorder defined as frequent and persistent difficulty initiating, maintaining, or going back to sleep. A hallmark symptom of this condition is a sense of nonrestorative sleep. It is frequently associated with other psychiatric disorders, such as depression, as well as somatic ones, including immunomediated diseases. BDNF is a neurotrophin primarily responsible for synaptic plasticity and proper functioning of neurons. Due to its role in the central nervous system, it might be connected to insomnia of multiple levels, from predisposing traits (neuroticism, genetic/epigenetic factors, etc.) through its influence on different modes of neurotransmission (histaminergic and GABAergic in particular), maintenance of circadian rhythm, and sleep architecture, and changes occurring in the course of mood disturbances, substance abuse, or dementia. Extensive and interdisciplinary evaluation of the role of BDNF could aid in charting new areas for research and further elucidate the molecular background of sleep disorder. In this review, we summarize knowledge on the role of BDNF in insomnia with a focus on currently relevant studies and discuss their implications for future projects.