Purpose: Chiari I malformation has been defined as cerebellar tonsillar descent greater than 5 mm below the foramen magnum. Suboccipital decompression remains the mainstay of treatment for symptomatic patients. Other conditions sometimes have imaging features that mimic Chiari I malformation. These patients are at risk of misdiagnosis and mismanagement, including surgery that may be unnecessary or may even worsen the underlying condition. The aim of this study was to analyse a series of Chiari I malformation mimics and identify differentiating imaging features. Methodology: The mimics are categorised as post-traumatic cranio-cervical junction arachnoiditis, dural band, spontaneous intracranial hypotension, idiopathic intracranial hypertension, and cysts. Results: Five conditions that mimic Chiari I malformation with features of cerebellar tonsillar descent have unique and distinctive imaging features. Conclusion: Recognition of these features will assist with prompt and correct diagnosis of Chiari I malformation. Furthermore, this will enable the delivery of optimal management, which includes avoiding unnecessary surgeries that may worsen symptoms and the underlying condition.