Current radio frequency radiation exposure guidelines rest on well-established thermal effects. However, recent research into analogue and digital transmission fields at levels covered by the exposure guidelines has indicated possible detrimental effects on human cognitive performance. To investigate this, we conducted a controlled climate chamber study of possible changes in cognitive performance in healthy volunteers exposed to transmission signals from TETRA hand portables (TETRA handsets). The trial deployed a balanced, randomized, double-blinded cross-over design. Performance on different paper-and-pencil, auditory and computer-based cognitive tasks was monitored in 53 male volunteers (mean age 36.41 years, SD 8.35) during 45-min exposure to a TETRA handset and sham control signals remotely controlled from a laboratory more than 100 km away. The main cognitive outcome was the Trail Making B (TMB) test. In addition, the participants completed a computer-based questionnaire measuring self-reported psychological and physical symptoms. No statistically significant differences (P < 0.05) between the TETRA and sham conditions were found for either TMB (estimated difference 3.8%, confidence interval (CI) -1.6% to 9.2%) or any of the remaining cognitive tasks or symptoms. In conclusion, we found no evidence that brief exposure to hand-held TETRA transmitters' affects human cognitive function or subjective symptoms.