Background: Although described as non-progressive, alternating hemiplegia of childhood (AHC) can display a sudden deterioration, anecdotally reported mainly in childhood. Outcome in adulthood is uncertain. Objectives: Aim of this study is to describe the long-term follow-up of neurological function in adults with AHC. Methods: Seven adults with AHC were included in this retrospective single-center study. Clinical history and previous investigation data were gathered from the review of medical records. Video-documented neurological examination was performed at the last follow-up visit in four out of the seven reported indivisuals. Results: Over a median follow-up of 16 years, neurological outcome and trajectories were heterogeneous. All individuals showed new neurological signs or symptoms. Three experienced a serious irreversible neurological deterioration after prolonged quadriplegic episodes and/or status epilepticus in their second or third decade. One patient died at age 29. Conclusions: This video-series suggests that AHC in adulthood is not stationary; larger cohorts are needed to identify genotype–phenotype correlations and clinically useful outcome predictors.