Combat is one of the aspects of gameplay engineered into Mother 4. It chiefly involves fighting enemies until either the enemy or all player characters run out of Hit Points, suffer a severe status effect, or run away.
Like the system in the official Mother games, Mother 4 is a turn-based front-view battle system where the current values of the player characters' Hit Points (HP) and Psychic Points (PP) are displayed, as well as their name. There is still a party of four player characters maximum, and it uses the traditional formatting of the attack commands:
- Bash - Selecting this will initiate a combo for that player character's turn, dealing physical damage to the enemy.
- Ability (PSI/Talk) - Selecting this will enable the player character to use their ability.
- Goods - Selecting this grants access to that player character's goods menu.
- Guard - Selecting this will increase the player character's resistance to physical damage for one turn.
- Run - Selecting this attempts to end the battle.
Like in Mother 3, all characters will be able to deal multiple hits to the musical coordination (Sound Battles). Also like in Mother 3, each player character has an ability. Travis, Meryl, and Leo have the ability of PSI, while Floyd has a "Talk" ability with various uses, including chatting with the enemy (using up turns for both him and the enemy), perking up party members, and bribing the enemy to stop fighting. Also returning are rolling HP and PP meters, which enable player characters to heal even if they have suffered mortal damage.
To enter battle, the player character (again) must contact the enemy. Like in EarthBound and Mother 3, this can be done by engaging the enemy head-on (creating a blue swirl), having the enemy contact the character from behind (creating a red swirl), or sneaking up on the enemy from behind (creating a green swirl).
The most notable difference in Mother 4's battle mechanic is the addition of a new meter and a GROOVY! bonus. When the meter hits its maximum, the bonus will activate, and the player character will be able to take an extra turn. Another difference is that instead of rewarding player characters with spikes in damage for every eighth, twelfth, and sixteenth hit when comboing, there is a chance of getting a SMAAASH!! hit for every hit, instead of just the first one.