Team Fortress 2 is played competitively on a varied number of modes ranging from 1vs1 to 9vs9, with many different intricacies such as class limits or team compositions, map pools, rulesets, etc.
- Main article: 6v6
6v6 is considered by most to be the staple competitive format, with the most skilled players competing and arguably the most competitive format with the most refined metagame. This format generally utilizes class limits of 2 on all classes save for Demo, Medic, Heavy, which have a class limit of 1 (this can vary depending on the league and ruleset of the league). 6v6 is mostly played on 5CP maps,as well as King of the Hill (KOTH) and Attack/Defense (A/D) maps.
- Main article: Highlander
Highlander, also known as 9v9, is another popular form of TF2. The format is mostly played in UGC and ETF2L. This format is played with class limits of 1 for all classes, with far more lenient weapon bans than 6v6 in most cases. Highlander is played on payload, KOTH, 5CP, and A/D maps. This format is generally accepted as the entry format to competitive tf2 as it has less entry barriers and is the format that best emulates pub play.
A format popularised by the Kritzkast Lo-fi Offclass Cup, where a 6v6 format game is played, but with the Scout, Soldier & Demoman classes being banned from competition. (Video)
- Main article: Prolander
Prolander is a 7v7 gamemode where each team has, at most, one of any particular class. The gamemode promotes prolific switching between classes as certain situations call for certain resources. Most commonly, a team will run one each of Scout, Soldier, Demoman, Medic, Sniper, and have two extra players switching between utility classes, rarely with Scout or Soldier replaced too. Currently, only RGL.gg supports the format. Also supports players with little-to no competitive experience.
- Main article: 4v4
4v4 is a competitive format featuring four players on each team, focused around KOTH and CP maps. Class limits are set to 1, with an additional restriction of 1 Heavy or Medic per team. Medics, Demomen and Scouts are commonly seen in this format, with Pyro and Soldier appearing quite often as well. The format has seen three One Night Cups, as well as an ongoing 5-week league. UGC announced the start of its first 4v4 season in January 2014.
- Main article: Ultiduo
Ultiduo is a competitive format consisting of two players on each team, usually a Soldier and a Medic. The objective is similar to King of the Hill, capture and defend the point from the opposing team. To win, you must run down the timer, which is done so by capturing the point. Since this gamemode consists of only a Soldier and Medic, it is heavily reliant on deathmatch skills.
- Main article: BBall
BBall is often considered the "bar pool" of TF2, as many high and low level players across different leagues play it, and little infrastructure is needed to start games or tournaments in it. The game is played on a replication of a basketball court, with the intel being used as a ball. Players must use a combination of rocket jumping and DM to take the ball from their opponents, and jump into (on top of) their hoop while holding it. The ball initially spawns in the center of the court. When a side scores a point, the intel spawns near the opposite sides hoop, giving the team (to most recently lose a point) an advantage in the next play. The majority of weapons are banned in BBall, usually save for the Original, and in some cases the Escape Plan and Gunboats.
No Restriction 6v6
- Main article: No_Restriction_6v6
No restriction 6v6 is an experimental competitive format featuring six players per team with no class limits or weapon bans. It is run by RGL and it's debut season began on the 12th March 2019 in North America. The format is designed to 'overthrow the meta' and (in the first season) teams were actively encouraged with rewards to use non standard lineups. Maps are also highly varied, with 5CP, KOTH and Payload all being played. A common theme among the Invite teams was to run two Medics with a variety of other classes, but it is possible to use any combination of classes, for example, six Airstrike Soliders or three Medics and three Demos, and the classes used would often shift significantly as a match progressed. The general idea behind the format was to start with a blank slate and see what new metas or tactics were established. This information could then be used to shape the format further, and/or be passed onto Valve for development of their in game competitive system.  The format expanded to Australia in the form of a one day cup on the 18th of April 2020. 
- Main article: MGEMod
One of the only established forms of 1v1 competition in TF2, MGE is a mod that offers players the chance to play 1v1 games where the first to a given number of frags (usually 20) is the winner. This format is more popular among Soldiers, and less commonly among Scouts and Demomen. It is used both as a common form of practice, and as a competitive format in and of itself. There are multiple populated MGE servers in all regions where players can practice their skills for use in various other competitive formats. Since May 2013, the MGE mod was updated to also support 2v2, which tries to simulate more of a 6v6 environment.
Ready Steady Pan
- Main article: Ready Steady Pan
Ready Steady Pan (RSP) is an introductory derivative of 6v6. It is played like any normal match, but with the players on each side using only the Frying Pan, among some secondary and jumper weapons for rollouts and movement. Heavies, Engineers, Medics, and Spies are disallowed in this game format.
- Main article: KnightComp
KnightComp is a derivative of 6v6. It is played just like normal 6v6, but the classlimits and weapon bans are very different. Demoman has no classlimit and Demoman players are not allowed to use any form of Stickybomb-type weapon. Medic and Soldier are both allowed at a maximum of 1 each. All other classes are disallowed in this format. This results in each team running at least 4 Demomen who are either Full Demoknights or Hybrid Demoknights. The KnightComp League aims to be the permanent home of competitive Demoknight.
- Main article: National Heavy Boxing League
Heavy Boxing is a 1v1 TF2 e-sport where two Heavies melee each other in a ring until one is killed. There are various melee weapons and formats used across the community for Heavy Boxing. The National Heavy Boxing League is the highest level of this e-sport.
There are plenty other competitive game modes that have not been explored to its full potential or haven't worked out in a competitive setting.