This study aimed to investigate trunk position sense, postural stability, and spine posture in women with fibromyalgia syndrome (FMS). Fifteen (15) women with FMS and age- and gender-matched fifteen (15) healthy controls were included. Trunk position sense as indicated by trunk reposition errors (TRE) and spine posture (thoracic and lumbar curvature) was measured with a digital inclinometer. Postural stability [eyes open (EO) and eyes closed (EC) on bipedal stance (BS), EO on monopedal stance (MS), and limits of stability (LOS)] was assessed with a computerized stabilometer (Prokin, TecnoBody S.R.L., Dalmine, 24044 Bergamo, Italy). TRE (p = 0.002) and the angle of thoracic curvature (p = 0.009) were found higher in women with FMS compared to healthy controls; however, the angle of lumbar curvature was similar (p = 0.467). It was seen that women with FMS had higher anterior-posterior sway in EO-BS (p = 0.009) and EC-BS (p = 0.001), ellipse area in EC-BS (p = 0.015), EO-MS of the dominant side (p = 0.021), and EO-MS of the non-dominant side (p = 0.007), and medial-lateral sway in EO-MS of the dominant (DM) side (p = 0.004) and the non-dominant (NDM) side (p = 0.002). Ellipse area in EO-BS (p = 0.054), medial-lateral sway in EO-BS (p = 0.983) and EC-BS (p = 0.290), anterior-posterior sway in EO-MS of the DM (p = 0.059) and the NDM side (p = 0.065), and LOS did not differ between groups (p = 0.274). Women with FMS had poor trunk position sense and postural instability, and alterations in spine posture. Therefore, the training of trunk position sense, postural stability, and posture might be beneficial and, thus, should be considered while planning an optimal treatment.