The purpose of the study was to design two cognitive behavioral treatments (CBT) for people with fibromyalgia (FM): therapy with electromyographic biofeedback (T1) and therapy without biofeedback (T2); and to assess their effects on psychopathological symptoms. The study was carried out with 88 people diagnosed with FM, aged between 26 and 65 years; 33 received T1, 33 received T2, and 22 were assigned to a control group without treatment. An evaluation was performed before and after a treatment of 10 sessions with the “Symptom Checklist-90-Revised,” the “State-Trait Anxiety Inventory,” the “Beck Depression Inventory” and “State-Trait Anger Expression Inventory”. The results showed that participants who had received a treatment decreased symptoms of hostility, state-anxiety, trait-anxiety, depression, trait-anger, and anger expression (p< .05). The effects of the two treatments were similar, and no significant group differences were found for any variable. The control group decreased less the symptoms, increasing anxiety and anger. This work provides an efficacious tool to reduce psychopathological symptoms and negative feelings in people with FM.