The aim of our study was to determine the effect of a cooling jet on performance and comfort in warm office environment. We compared cognitive performance, subjective workload, cognitive fatigue, thermal comfort, symptoms, perceived working conditions and perception of airflow in warm temperature (29.5 °C) in two conditions: with and without the jet. Twenty-nine students participated in the experiment in which a repeated measures design was employed. The jet improved the speed of response in a working memory task with increasing exposure time but did not affect other performance measures. Self-rated performance was higher and frustration was lower with the jet. Tiredness increased with increasing exposure time without the jet, but remained constant with the jet. Thermal comfort and perceived working conditions were improved, and indoor air was perceived fresher with the jet. Eye symptoms increased over time with the jet. The results support the use of cooling jet in offices with high thermal loads where individual control over the air temperature is not possible via air conditioning. It seems, however, that there is a need for individual control over the jet already when the target velocity is set to the upper limit according to ASHRAE standard.