Even while solving a case, Heiji tends to be lighthearted and good-humored, preferring to work through it with a grin on his face. He is a big fã of baseball, and is most of the time shown wearing an Osaka cap, to support the local Osaka baseball team. He usually wears his boné, cap with its visor pointed backward, but if he feels challenged, he turns the visor forward.

Heiji is known for his pride as an Osaka citizen and for his thick Osakan accent, which has been pointed out and sometimes made fun numerous times. However, Heiji holds his head high and is always one to brag about the greatness of Osaka, especially when Conan comes to visit.

Despite him knowing the value and necessity of remaining calm in the face of a crime, Heiji tends to be impulsive at times, which tends to nuvem his judgment a little. This was discussed directly in the "Detective Koushien" case, when Saguru Hakuba accused Heiji of being a poor detective for disrupting a crime scene in his rush to see if the victim could still be saved. Heiji, however, solved the case in the end, and reminded Saguru that the detective's first job is to prevent death if he can.