Few studies focus on the mechanisms that regulate consistent individual-level differences in behaviour (i.e., personality) in wild animals, despite their potential evolutionary and ecological implications. I examined whether wild checkered pufferfish (Sphoeroides testudineus) have consistent individual-level differences in locomotor activity, threat-response behaviour, swimming ability, and puffing performance. I also evaluated the relationships between these personality and performance traits. Personality and performance were compared to movements in the field. In addition, I tested whether a treatment of the stress hormone cortisol would alter personality and performance. Pufferfish exhibited personalities but these were not associated with performance or recapture in the field. Performance was consistent between the lab and the natural enclosure but activity was not. The cortisol treatment did not modify personality or performance, which suggests that these traits do not represent a stress-coping syndrome. I conclude by recommending future directions for research on stress and personality in wild animals.