The ISTJ type's inclination toward loyalty and dedication definitely translates to their relationship lives. Blaylock-Solar notes they make loyal, trustworthy, and dependable partners. "You can count on their commitment, whether in romantic or platonic relationships. They are invested in the satisfaction of their partners," she says, though she adds, "However, they are not very spontaneous."
While generally good partners, it may just take a little extra time to get these people to open up. As Hackston explains, "People with ISTJ preferences are private and not always easy to get to know, but once they are in a relationship, they are very committed."
He adds that they tend to take on a traditionally gendered role, and assume or expect that their partner will do likewise. "They appreciate dependability and reliability and will try to make sure their significant other feels heard. On the other hand, they will probably have a hard time dealing with drama," he explains.
In terms of MBTI compatibility, Hackston notes that the ISTJ type meshes well with others who have the same sensing-thinking preferences (AKA practical, factual, and direct)—so ISTP, ESTJ, ESTP or another ISTJ.