The aim of this study is to evaluate and compare the immediate analgesic effects of two applications of short-wave diathermy (SWD) in individuals with chronic low back pain. Randomized, controlled, double-blind clinical trial. A total of 159 participants with chronic low back pain will be randomized in three groups: pulsed mode SWD, continuous mode SWD and placebo. SWD will be applied only once for 30 min. The primary outcomes: intensity and quality of pain. Secondary outcomes: depression and anxiety; perception of global improvement; patient satisfaction; disability and influence of psychosocial factors, strength of the lower limbs and the mobility of the posterior chain. Patients will be evaluated before and after the session and 1 week after. Trial registration number: RBR-2k58f5h Brazilian Registry of Clinical Trials (ReBEC).