Matt is Tai's opposite; while Tai is extremely impulsive and acts without thinking, Matt tends to think cautiously about a situation and choose a solution that would be the most practical. This can lead to disputes between the two about whether to take the most logical but not necessarily humane solution, or to go with emotion and choose the idea that seems most empathetic.
During Adventure, the two are on extremely tight terms. They often get into disagreements, which are not helped by Matt's "lone wolf" personality. Tai believed that Matt did not "understand" anything and thinks too much, and that his antisocial ways would not help the team at all. Despite this Tai does on occasion relent to Matt's point of view. When the group needs to get back to Highton View Terrace, Tai repeatedly denies requests to use their money to get food until Matt mentions he wants to as well. The reason for this is possibly because of Matt's practical reasoning as he does point out in this instance that their Digimon wouldn't be able to protect them if they are hungry as opposed to the others complaining. Similarly in the second episode of the series Tai is prepared to explore the beach until Matt says he's staying on the beach for a while because even if they can't phone anyone, someone may be able to call them.
In Adventure 02, Tai and Matt are on much better terms. At one point, Matt punches Tai in order to snap him back to reality, and Tai thanks Matt for doing so. They consider each other to be best friends and attribute this to the fact that they fought a lot when they were younger.
Sora and Tai had been classmates prior to Adventure and were already friends with each other by the time the series had started. They also played on the same soccer team. Over the course of Adventure, Sora becomes an important person to Tai and the source of his distress when she is kidnapped by Datamon. Sora is also someone whom Tai often relies on, both for her opinion and for her reliability. In the episode in which Agumon digivolved to SkullGreymon, Tai asked Sora if he had gone too far in pushing Agumon to digivolve to Ultimate, and in several episodes Tai asks Sora to take care of certain things for him (for example, watching T.K. and Kari while he and Izzy looked for medicine for Kari, who had fallen ill, and finding Matt when Tai was facing Piedmon). In the beginning of Adventure, Sora often showed concern for Tai's bullheadedness, arguing with him when she thought he was being reckless. As Tai matures as a leader, Sora is more often seen actively supporting his decisions.
In Our War Game, Tai is seen trying to email Sora to apologize for a hairpin he had gotten her that offended her, and is distressed when it seems that the email can't be delivered. He also later confesses to Izzy that he already tried calling Sora many times to apologize, indicating how important it was to him that Sora forgive him.
During Adventure 02, Sora and Tai are slightly detached. However Sora still remains an important person to Tai and he seems willing to help her when she has problems, such as when she wanted to confess to Matt that she had romantic feelings for him.
During the first season while Tai likes to mock Izzy for carrying his computer around, he does indeed understand Izzy's ability to think through things and process facts. Tai often looks to Izzy as his closest ally in situations (particularly when his relationship with Matt turns sour) such as when Sora is held hostage in Etemon's pyramid, Tai chooses Izzy to accompany him into the pyramid. Tai also looks to Izzy as his immediate partner to accompany him to find medicine when Kari becomes ill. When Tai recognizes Izzy's capacity to figure out the code of the cards to get them back home he admits that Izzy has a better intellect than himself.
In the Digimon Adventure PSP game, it is stated that Izzy is Tai's best friend, although Tai has punched him when angry.
Tai was also the one to invite Izzy to summer camp, since Izzy was in the soccer club.
While Tai sees Mimi as a fragile pacifist, he seems to trust in her opinion. Similar to Sora, Tai considers Mimi an important person and valuable to the team. He also occasionally goes to her for solace. Mimi is also the one who cheers him up since he mistakenly forced Agumon to dark digivolve to SkullGreymon, Tai returns the favor by forgiving her actions at ShogunGekomon's Castle.
Tai sees Joe as a source of practical know-how and as someone who can be relied upon to take care of the team.
In the beginning of Adventure, whenever Matt is not around, Tai acts as the missing older-brother figure to T.K. However, as the series progresses, Tai exhibits more of this behavior more often, leading to tensions with Matt.
In Adventure 02, Tai believes T.K. to have grown up enough and thus lets him have his own responsibilities.
As Kari's brother, Tai feels responsibility for Kari's well-being, something that escalated when Tai wanted to play with Kari as a young child and ended up giving her pneumonia. This leads to a paranoia of sorts, as he eventually becomes so overprotective of her that he begins to believe anything should be sacrificed for the sake of his sister.
In Adventure 02, Tai places more trust in Kari, but still shows some protective tendencies. Like the other DigiDestined, he tries to prepare Kari and her team for the possible need to actually kill evil Digimon, as the new DigiDestined are not used to Digimon who are malicious of their own free will.
To Tai, Davis is his protégé. Since Tai has entrusted taking care of a DigiDestined team to Davis, he passes on his beloved goggles to him as a symbol of such. Tai occasionally oversees everything that Davis does to make sure he's doing it right, and is always willing to offer advice.
Tai sees Yolei as the more excitable girl of the group.
Tai sees Cody as the "straight man" of the group.
Tai is often willing to assist Ken in times of need and help him get over his stress over having been the Digimon Emperor.