This review is intended to provide an updated summary of, but not limited to, classification, etiopathogenesis, diagnosis, and treatment strategies for insomnia disorder. The severity of insomnia symptoms irrespective of co-existing primary medical condition/s in the studied patients classified insomnia as 'insomnia disorder' to prioritize the clinical attention on insomnia (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition). The frequency and duration of symptoms further divided insomnia into chronic, short-term, and other insomnia disorder (International Classification of Sleep Disorders, Third Edition). This disorder is a phenomenal state of hyperarousal developed and perpetuated by environmental, behavioral, cognitive, genetic, socioeconomic, preexisting medical factors. Overarching physiological, cortical, behavioral, and cognition changes in hyperarousal manifest insomnia disorder. It, sometimes, leads to the co-occurrence of other chronic medical condition/s. The contemporary diagnosis of insomnia disorder needs to consider modified diagnostic criteria, growing evidence on insomnia disorder symptoms, associated factors, co-existing medical condition/s (if any) to identify the subjective severity of insomnia disorder and design a treatment plan. The recommended treatment strategies include cognitive-behavioral therapy for insomnia (CBTI) and pharmacotherapy. However, CBTI lacks accessibility, qualified facilitators, and pharmacotherapy has limitations like side effects, physiological tolerance/dependence. The investigation of phytocompounds subdued these drawbacks of existing treatments as some compounds showed anti-insomniac potential. Furthermore, complementary alternative medicines (CAMs) like mindfulness-based practices, acupuncture, listening to music, Yogasanas, Pranayama, digital cognitive behavioral therapy for insomnia (dCBTI) during bedtime proved supportive in insomnia disorder treatment.