Objectives To determine the prevalence and characteristics of post-COVID-19 (PC) in fibromyalgia (FM) patients. Methods Retrospective, multi-centric, observational study, comparing a group of FM patients (FM group) with another group of patients with other rheumatic diseases (RD group). COVID-19 diagnosis was established by positive polymerase chain reaction or antigen during acute infection or by positive antibodies thereafter. We considered PC diagnosis when symptoms remain after COVID-19. We collected the principal characteristics of COVID-19, the severity of fatigue, waking unrefreshed and cognitive impairment, and persistent symptoms. The American College of Rheumatology (ACR) criteria and the Combined Index of Severity in Fibromyalgia (ICAF) were collected in the FM group. Results RD group (n = 56) had more pneumonia (p = 0.001) and hospital admissions (p = 0.002), but the FM group (n = 78) had a higher number of symptoms (p = 0.002). The percentage of patients with PC was similar between groups (FM group 79.5%; RD group 66.1%, p = 0.081). FM group had more PC symptoms (p = 0.001), more impairment after COVID-19 (p = 0.002) and higher severity of fatigue, waking unrefreshed and cognitive impairment (p <  0.0001). Only loss of smell was more frequent in the FM group (p = 0.005). The FM group with PC (n = 29) showed more severity of the Combined Index of Severity in Fibromyalgia (ICAF) total score and physical factor after COVID-19, while emotional, coping factors and the ACR criteria did not change. Conclusions The prevalence of PC in FM patients is similar to RD patients. In FM patients, the presence of PC does not appear to impact the severity of FM.