To determine if ultrasound (US) is effective in reducing pain and mobility limitation in the treatment of traumatic cervical sprain, we performed an experimental study. The sample comprised 54 diagnosed subjects with a mean age of 36.54 y (standard deviation = 12.245), assigned by simple random selection to an experimental group with ultrasound treatment and a control group with placebo ultrasound. Treatment consisted of 10 sessions of an ultrasound treatment protocol, followed by 15 sessions of a protocol identical for both groups without ultrasound. The variables assessed were pain and joint mobility. There was no significant difference (p>0.05) between groups in the first 10 sessions of treatment. However, there was a statistically significant difference (p<0.05) between groups on the pain variable, 20 days after completion of the US. High-active ultrasound treatment is more effective than placebo in reducing pain.