Oral mucositis (OM) is a serious and acute side effect in patients with cancer who receive chemotherapy or radiotherapy, often leading to the suspension of therapy and a need for opioid analgesic and enteral/parenteral nutrition, with an effect on patient survival. Among the various interventions proposed in OM management, laser therapy is becoming a recommended treatment option but has limitations due to its heterogeneous laser parameters. Here, we report on our successful clinical experience on the use of class IV laser therapy to treat OM induced by different chemotherapy regimens. To shed light on the mechanisms of action of laser therapy in improving OM resolution, we have developed an animal model of chemotherapy-induced OM, in which we compare the efficacy of the standard low-power laser therapy protocol with an innovative protocol, defined as high-power laser therapy. We show that high-power laser therapy is more effective than low-power laser therapy in improving OM lesion healing, reducing the inflammatory burden, and preserving tissue integrity. In addition, high-power laser therapy has been particularly effective in promoting the formation of new arterioles within the granulation tissue. Our results provide important insights into the mechanism of action of biostimulating laser therapy on OM in vivo and pave a way for clinical experimentation with the use of high-power laser therapy.