Abstract Background Postpartum septic symphysitis (PPSS) is defined as acute onset of severe pain around the symphysis, restricted movement, fever, and elevated inflammatory parameters. It is a rare but serious condition requiring urgent diagnosis and treatment. The aim of this study was to describe the incidence, symptoms, diagnosis, treatment, and long-term follow-up of PPSS. Methods This follow-up study included 19 out of 21 women diagnosed with PPSS from 1989 to 2017 at one tertiary care hospital in Sweden. Clinical data were retrieved from hospital records and compared to those retrieved from a regional registry. Women completed a postal questionnaire, and those who reported lumbopelvic pain (LPP) were offered a clinical examination. Results 1) PPSS was diagnosed after a normal postpartum period of 24 to 50 h by blood tests (n = 19/19), ultrasonography (n = 9 /19), computer tomography (n = 8/19) or magnetic resonance imaging (n = 16/19) Treatment included aspiration of symphyseal abscesses, i.v. antibiotics and different physiotherapeutic interventions. Women with PPSS more frequently were primiparous (n = 14/19, p = 0.001), had an instrumental delivery (n = 14/19, p = 0.003), longer time of active labour (p = 0.01) and second stage of labour (p = 0.001) than women in the regional registry. 2) Ten out of 19 (52%) women reported LPP at follow-up. These women more often suffered impaired function related to LPP (Pelvic Girdle Questionnaire, 27 versus 0, p