Editing Mario Tennis: Ultra Smash

|align="left|Drop Shots are low shots with a low bounce aimed at the front of the court. The Chance Shot version does not bounce. They leave a white trail and have the outline of a [[Bob-omb]] in the Chance Shot area.

|align="left|Simple Shots are version of all the five shot types that take longer time to charge, chosen automatically once the button for the Simple Shot is pressed. They can be used on Chance Shot areas as well, resulting in the correct type of shot being chosen automatically. They leave a light yellow trail.

Knockout Challenge is a single-player mode that replaces the Tournament modes from earlier installments of the ''Mario Tennis'' series.<ref name="Hands on Preview"/> Players try to beat an increasing number of CPU opponents, who gradually get harder over time.<ref name=NWR/> The order of opponents is as follows: Toad, Luigi, Daisy, Yoshi, Wario, Sprixie Princess, Toadette, Boo, Peach, Waluigi, Donkey Kong, Bowser Jr., Rosalina, Mario, and Bowser (Dry Bowser in the 2nd sequence). Then the sequence repeats. After the 2nd sequence, the opponents will be randomized (though they will never face the same opponent more than once in a row). If the player uses Toad or has Toad as an amiibo partner, the CPU-controlled Toad is substituted with Toadette. If the player uses one of the other characters or has one of the other characters as an amiibo partner, that character in the sequence is replaced by Toad. If the player uses Bowser or has Bowser as an amiibo partner, the CPU-controlled Bowser is substituted with Dry Bowser. If the player uses Dry Bowser, the CPU-controlled Dry Bowser is substituted with Bowser. If the player uses Dry Bowser and has Bowser as an amiibo partner, the CPU-controlled Bowser and Dry Bowser are substituted with Bowser Jr. The matches, by default, are Mega Battles (and Standard Tennis after the 2nd sequence) with Tiebreaker rules; the player has to win seven rounds in order to claim game victory. With every battle won, players earn [[coin]]s, which can be spent on buying unlockables, such as star characters and courts.<ref name=NWR/> amiibo characters can help the single players out; however, other human players cannot help the single-player.

Online can be played alone or with another player or amiibo character in Singles or Doubles. The game does not support lobbies or communities, whereas the only options are Singles and Doubles.<ref name=NWR/> Similarly to ''[[Super Smash Bros. for Nintendo 3DS / Wii U]]'', online play is split into two categories: Play for Fun and Play a Serious Match. Play a Serious Match lets players play in ranked settings to grow their standing compared to their online opponents, whereas Play for Fun still sets up matches based on online ratings, but these ratings are not affected in this mode.<ref name=NWR/> Players can choose to play a Mega Battle, Standard match, or Simple match.  They can also choose whether to play a tiebreaker game or a two-game, one set match. The game featured worldwide online multiplayer for the first time in the ''Mario Tennis'' series, after ''Mario Tennis Open'' introduced online play locked to the player's region.<ref>{{cite|author=@NE_Brian|date=February 6, 2016|url=nintendoeverything.com/mario-tennis-ultra-smash-team-on-hd-development-new-characters-amiibo-and-online-play|title=''Mario Tennis: Ultra Smash'' team on HD development, new characters, amiibo, and online play|publisher=Nintendo Everything|accessdate=May 14, 2024}}</ref>

Players can tap any compatible amiibo figurine into the game to help players out in Knockout Challenge and online play. When amiibo level up after completing a set number of matches, a random stat out of the eight stats gets enhanced. In addition, each stat has its own slot limitations: for example, an amiibo character cannot have more than three speed stats in their inventory. Once all ten stat slots are filled, the amiibo cannot obtain any more stats though players can remove gained stats for a fee of 5,000 coins, so the slot can be filled by another stat. These are the following stats that can be enhanced: