INTJ vs ISTJ – The Difference between these Two Personality Types

As logically-based, intellectually-oriented introverts, it’s not surprising that the INTJ type and ISTJ type often get compared to and sometimes confused with each other. They are both planners and organizers and usually have a very strong work ethic. If they could, they would spend as much time as possible seeking to improve the lot of others in the world.

But they have a fair amount of differences.

Key Differences between INTJs and ISTJs

One of the key differences between INTJs and ISTJs is that INTJs are highly creative and like to use their imagination, whereas ISTJs like to deal in facts and details. Another key difference is that INTJs like things loose and are not fans of authority, while ISTJs like structure and rules.

Both INTJ personality type and the ISTJ personality type tend to have driven personalities with one track minds that allow them to become completely focused on what they are doing. Perfectionism can be an issue for both the INTJ type and ISTJ type. In their personal lives, they are very private people who tend not to be very self-reflective. They may both struggle in dealing with the emotions of others as well as their own emotions.

A closer examination of both personalities, however, reveals that they have many differences. Here are just a few:

  • The INTJ personality is all about theorizing — the more creatively, the better.
  • The ISTJ personality prefers to deal with specific facts and details rather than using their imagination.
  • INTJs prefer a loose work environment with few rules and expectations.
  • ISTJs will do best in a more structured work environment. 
  • INTJs bristle under any type of authority and will tend to challenge those looking to take charge.
  • ISTJs have no problem working within a hierarchy or under any type of authority.
  • An INTJ personality type looks to the future and are always open to new and better ways of doing things. Change invigorates them.
  • An ISTJ person prefers tradition and will often hesitate to change anything in their lives.
  • INTJs memories tend to be more like abstract impressions rather than specific details of the events from their past.
  • ISTJs usually have very sharp memories and can even recall moment by moment facts of what exactly happened.
  • INTJs want to be happy in their work life above all else and won’t hesitate to quit if they are unhappy.
  • ISTJs may stay at a job even though they are unhappy, reasoning that change wouldn’t be worth it.

Cognitive Functions for ISTJ vs INTJ Personality Types

Each personality type has four unique cognitive functions — Intuition, Thinking, Sensing and Feeling. Each of those functions can be further broken down into Extroverted (expressed outside of the individual’s mind) or Introverted (expressed inside of the individual’s mind.)

When you look at INTJs and ISTJs specifically, the reason they are so similar is that they share two of the same cognitive functions, the auxiliary and the tertiary function. Their dominant function is different, however, which explains why they absorb information differently. Their inferior function is also different, which is discussed below.

ISTJ vs INTJ Dominant Functions:

An INTJ’s dominant function is Introverted Intuition, meaning they will focus on the bigger picture and always have their eyes toward the future.

An ISTJ’s dominant function is Introverted Sensing, meaning they will tend to be detail-oriented and focused on the present.

INTJ vs ISTJ Auxiliary Function:

Both personalities share Extraverted Thinking as their auxiliary function. This means that they are both rational and methodical in their thought process and in their actions. They tend to be impersonal and even non-emotional at times because they are so deeply committed to solving the problem at hand.

INTJ vs ISTJ Tertiary Function:

Both personalities share their tertiary function, as well, which is Introverted Feeling. This means that they both have a moral code that dictates to them what is right and wrong. They feel compelled to live by these values, especially ISTJs, and when they stray from them, they feel a sense of guilt or unease.

ISTJ vs INTJ Inferior Function:

An INTJ’s inferior function is Extraverted Sensing, which involves their perception of the physical world.

An ISTJ’s inferior function is Extraverted Intuition, which involves making theoretical connections based on conditions in the physical world.

INTJ Personality Type Dominant Function

An INTJ’s dominant function of Introverted Intuition means that they are full of ideas and theories. They can get totally lost in their thoughts as they conceive better ways of doing things with the goal of helping humanity. Here are some of the ways INTJs express their Introverted Intuition:

  • They spend a lot of time imagining possibilities that the future may hold.
  • They are life-long learners and are especially voracious readers.
  • They are excellent problem solvers with a particular knack for discerning patterns that other people might not see.
  • They tend to concentrate on what information means rather than just the data itself.

An INTJ’s auxiliary function is Extraverted Thinking. Thus, they are logical and orderly in their approach to theorizing and problem solving. Here are some of the ways INTJs express their Extraverted Thinking:

  • They prefer a loose framework when working, so long as it was created by them and hasn’t been imposed by an authority figure.
  • They are very much interested in cause and effect relationships and will frequently point out the difference between causation and correlation when making intellectual arguments.
  • They generally have no problem making decisions.

An INTJ’s tertiary function is Introverted Feeling which involves that nagging bit of emotion that lies in the back of an INTJ’s mind. It tends to be more developed in an older or more mature individuals. Here are some of the ways INTJs express their Introverted Feeling:

  • While they will always use logic when making decisions, this aspect of their personality may make them err on the side of what lines up with their own values if it is logically permissible.
  • They usually dislike talking about their emotions, but with the right people in the right circumstances, they can learn to open up a little bit.

An INTJ’s inferior function is Extraverted Sensing which is gathering information about the world via one’s senses. Given this is an inferior function, it may be one of the weaker aspects of the INTJ’s personality. Here are some of the ways INTJs express their Extraverted Sensing:

  • INTJs may be more in tune with their environment than other people — they will gather information and then spend time determining what the information may mean.
  • Most of the time, an INTJ is thinking about the future. This cognitive function, however, tends to pull them toward thinking about the present. If this aspect of their personality is allowed to strengthen, they may find more balance in their lives.

ISTJ Personality Type Dominant Function

  • They are planners. They use all gathered information in order to come up with the best possible plan.
  • They are experts at prioritizing. ISTJs know what needs to be done and when it needs to be done to maximize efficiency.
  • Part of the information they gather has to do with what has worked best in the past. They have excellent memories and will tend to rely heavily on tradition and precedence.
  • They are willing to trust other people’s expertise and incorporate these expert ideas into their own planning.

An ISTJ’s auxiliary function is Extraverted Thinking. This means that they are on the ball. Not only are they intelligent sponges of information but they use this information in a logical and rational way. Here are some of the ways INTPs express their Extraverted Thinking:

  • They are very methodical and usually use a step-by-step approach to problem solving.
  • They tend to immerse themselves in details and will struggle to see the bigger picture.
  • They are unafraid of making decisions and will consider facts rather than emotions.

An ISTJ’s tertiary function is Introverted Feeling. This may be the reason that some may see them as being judgmental. They are constantly measuring people and actions against their own rigid value system. Here are some of the ways ISTJs express their Introverted Feeling:

  • They are known for their intuition or “gut feelings” about situations and people. They will make decisions using this intuition and will, more often than not, be right.
  • Some people might accuse ISTJs of being closed-minded and not open to people or ideas that or unknown to them.

An ISTJ’s inferior function is Extraverted Intuition. Thus, there is a small part of an ISTJ that enjoys new experiences and taking risks. This part of their personality usually needs to be developed in order to shine, however. Here are some of the ways INTPs express their Extraverted Intuition:

  • They get bored easily and would prefer doing something active rather than just sitting around.
  • They tend to have a lot of hobbies, many of which may revolve around being physically active.

INTJs and ISTJs — Conflict between the two

INTJs and ISTJs both value logic and have a rational approach to problem solving. Their methods of decision making are very different as are their general perspectives on the world. These differences could prove to be difficult if the two were in a situation were cooperation was important.

What might INTJs and ISTJs fight about?

An ISTJ needs to make certain that all of their actions and decisions conform to their sense of right and wrong. This will undoubtedly irritate an INTJ who would rather not be stifled by any external standards.

Both personalities love intellectual debate. INTJs may take it too far for an ISTJ, however, who could end up feeling personally attacked even though the INTJ never had that intention.

The INTJ’s out-of-the-box and future-aimed solutions might be very hard to fathom for an ISTJ who relies on tradition and conventional wisdom to guide their lives. It may be hard for them to reconcile their different approaches if they had to work together.

Here are two examples of real life problems that might cause these personalities to struggle:

  • If an INTJ and an ISTJ needed to come up with a policy for dealing with employee tardiness, the ISTJ would pore over all data regarding employee tardiness and would want to consider what methods of discipline had been effective in the past. An INTJ, on the other hand, would want to come at the problem in a new, sweeping way, throwing out past attempts to control the problem in order to invent some new incentive to coax the employees into behaving differently. It would all seem very whimsical and impractical to the ISTJ, whereas the INTJ would feel that the ISTJ’s solution was rigid and unimaginative.
  • If an INTJ and an ISTJ were in a romantic relationship with an eye toward marriage, they would need to have a heart to heart discussion about how they imagined their future. The INTJ would want to focus on their career and their far-out ideas about solving the world’s future problems. The ISTJ would want to start a family and have a home with a white picket fence. The question would be, how could these two reconcile both of their ideas of what the perfect married life would look like and stay together.