Ketogenic diets have been used to treat epilepsy in children for almost 80 years. However, there are only few studies concerning behavioral effects of these diets, besides their efficacy in treating seizure disorders induced by kainic acid or pentylenetetrazol in rats. Here, rats were fed with a ketogenic diet and locomotion, anxiety and nociception were investigated after 10 weeks. Male Wistar rats were weight matched and divided into two groups: control rats, that received regular laboratory ration, and KD rats, that received ketogenic diet (70% fat, 24% protein and no carbohydrate). Behavioral tests were applied after 10-12 weeks of treatment, and included tests to evaluate exploration (habituation to the open field), anxiety (plus-maze), and nociception (tail-flick measurement). Performance of the animals in the open field revealed a significant difference in the number of crossings, suggesting a higher locomotor activity in animals fed with a ketogenic diet. No differences in anxiety were observed, as evaluated by the plus-maze test. Nociception was measured by the latency in the tail-flick test, and ketogenic rats presented a hypernociceptive response. Yet, these animals responded to a stressor with the classic analgesia, similarly to the controls. The response of ketogenic diet fed rats to the stressor, however, was more prolonged. Exposure to a ketogenic diet may induce higher locomotor activity, together with a hypernociceptive state in the animals, possibly as a result of some alteration in the neural systems involved in the modulation of these behaviors.