Nausea and vomiting affect up to 80% of all pregnancies, sometimes so severely that the condition of hyperemesis gravidarum (HG) is established. HG may in addition be a predisposing factor for Wernicke encephalopathy (WE), a severe and life-threatening condition due to vitamin B1 (thiamin) deficiency. If untreated, WE may progress to Korsakoff's syndrome, an irreversible cognitive disorder. We reported a case that recently occurred at our clinic and performed a systematic review of the literature to investigate the clinical presentation, maternal and perinatal outcomes and treatment of WE in women with HG. We performed a systematic review of case series and case reports searching the Medline database on Pubmed from inception until December 2021. We used as search terms (Wernicke encephalopathy) OR (Wernicke-Korsakoff syndrome) AND (hyperemesis gravidarum) AND (pregnancy) AND (thiamin deficiency). Articles were considered eligible for inclusion in our review if they described at least one case of WE due to thiamin deficiency in relation to HG. An overall of 82 cases of WE due to HG in pregnancy from 66 manuscripts, including our own, were selected. The maternal mean age was 26.38 ± 5.23 years, while mean gestational week at hospitalization was 14.57 ± 4.12 after a mean of 6.6 ± 3.14 weeks of vomiting duration. WE manifestation occurred at a mean gestational age of 16.54 ± 3.06 weeks. Regarding clinical presentation, ocular signs and symptoms were reported by 77/82 (93.9%) women, 61/82 (74.4%) presented with ataxia and 63/82 (76.8%) with confusion. Dysarthria affected 15/82 women (18,3%), while muscular weakness was present in 36/82 (43.9%) and impaired reflexes in 42/82 (51.2%). Memory impairment involved 25/82 (30.5%) of the study population. Almost all cases reported a thiamin administration treatment, however data regarding the clinical course of the neurological condition and the perinatal outcomes were often missing and showed a great heterogeneity when reported. WE is a challenging diagnosis, as its clinical presentation is nonspecific. A high clinical suspicion and the awareness of its possible predisposing conditions such as HG may help clinicians to get a prompt diagnosis and starting treatment, which are vital to prevent possible life-impairing neurological sequelae.