question: Background: We analyzed the immediate effects of a Telerehabilitation Program (TP) based on aerobic exercise in women with fibromyalgia (FM) syndrome during the lockdown declared in Spain due to the COVID-19 pandemic. Methods: A single-blind randomized controlled trial was designed. Thirty-four women with FM were randomized into two groups: TP group and Control group. The intervention lasted 15 weeks, with 2 sessions per week. The TP based on aerobic exercise was guided by video and the intensity of each session was monitored using the Borg scale. Pain intensity (Visual Analogue Scale), mechanical pain sensitivity (algometer), number of tender points, FM impact (Revised Fibromyalgia Impact Questionnaire), pain catastrophizing (Pain Catastrophizing Scale), physiological distress (Hospital Anxiety and Depression Scale), upper (Arm Curl Test) and lower-limb physical function (6-min Walk Test) were measured at baseline and after the intervention. Results: The TP group improved pain intensity (p = 0.022), mechanical pain sensitivity (p < 0.05), and psychological distress (p = 0.005), compared to the Control group. The Control group showed no statistically significant changes in any variable (p > 0.05). Conclusions: A TP based on aerobic exercise achieved improvements on pain intensity, mechanical pain sensitivity, and psychological distress compared to a Control group during the lockdown declared in Spain due to COVID-19 pandemic.