Heiji is also known to be extremely protective of those he values as close friends, and tries hard to keep them out of harm. There are several instances where Hattori tells Kazuha to wait for him o leaves her behind in order to keep her from being involved in cases, simply because he's afraid of her getting hurt.

Furthermore, he's pretty much always watching Shinichi's back, and does whatever he can to not only keep Shinichi safe, but to keep his identity under cover. However, on one occasion Heiji advised Conan to tell the truth, when Ran had convinced herself that Conan was Shinichi and thus willingly gave him blood after being shot.

Although he is very competitive when it comes to detective cases, when a case gets hot, he and Shinichi work effectively together. During Shinichi's first return to his high school during the play performance, Heiji let him take the lead role in the investigations, saying it was because they were in Tokyo, Shinichi's turf.

Although he frequently mocks Kazuha for her superstitions and enthusiasm for good-luck charms, Heiji has several times revealed that he puts più trust in them than he would admit. He once dreamed of Shinichi being murdered, and out subsequently insisted that Conan wear his omamori, the good luck charm Kazuha gave him. The omamori ended up saving Shinichi's life da deflecting a coltello blow, but Heiji, without his usual protection, was shot in the stomach.