Photobiomodulation therapy (PBMT) can be applied to a tender area on a subject's body to treat fibromyalgia. A light source device can be contacted to a subject's skin proximal to a tender area on the subject's body. A light signal (with wavelengths from the red to infrared part of the spectrum) can be applied in at least one of a pulsed operating mode, a continuous operating mode, and a super-pulsed operating mode through the light source device to the tender area. The light signal is applied for a time sufficient to stimulate a phototherapeutic response in the tender area to treat fibromyalgia.