: Fibromyalgia syndrome (FMS) is a multifactorial pain syndrome not only characterized by widespread pain as the primary symptom but also accompanied by physical, psychological, and cognitive manifestations. Impairments in conditioned pain modulation (CPM) are common in this population; however, there is significant heterogeneity in the CPM response among women with FMS. The Left/Right Judgment Task (LRJT) is a validated method for studying motor imagery in chronic pain patients. Previous scientific evidence has not yet thoroughly investigated the relationship between CPM alterations and motor imagery processes in FMS patients. The aim of this study was to investigate the relationship between CPM and motor imagery. : This is a secondary analysis of a cross-sectional study. Pain intensity (NPRS), disability (FIQ), mechanical hyperalgesia (PPT), descending pain modulation (CPM), and laterality discrimination (LRJT) were assessed in 30 women diagnosed with FMS. Participants were divided into two groups, responder and non-responder, according to their response to the CPM test. : Findings showed that the FMS subgroup of non-responders to CPM, performed worse in motor imagery processes (LRJT). Additionally, older age and higher mechanical hyperalgesia were also associated with poorer functioning of the inhibitory system. : Women with FMS who are non-responders to CPM exhibit a reduced ability to perform motor imagery processes. Additionally, the non-responder group shown significant differences, such as older age and greater initial mechanical hyperalgesia compared to the responder group.