How to Beat Undyne in Undertale


Kenneth Mitchell

Writer and Storywriter


Undyne is the third boss in Undertale, and her boss fight may be tricky. Her attacks are very challenging to avoid, and you’ll end up taking damage. Even so, there are strategies to help you defeat her.

How to Beat Undyne in Undertale

As you can beat Undertale in Genocide or Pacifist Runs, the strategies will differ. We’ll include both to help you with both runs when you come back for the other. With these tips, Undyne the Undying won’t be too difficult of a match.

Genocide Run

In Genocide Runs of Undertale, your goal is to kill every living creature you see. This runs category includes the sweet Toriel and everyone else. Undyne the Undying isn’t an exception, and when you fight her, things can get complicated.

The best strategy is to stock up on healing items, speed items, and armor. Here’s a list of what we recommend:

  • Sea Tea for SPEED
  • A variety of healing items
  • Ballet Shoes weapon
  • Cloudy Glasses armor for more invulnerability frames
  • Torn Notebook weapon for more invulnerability frames, instead of Ballet Shoes

Fighting Undyne consists of avoiding arrows and spears. Initially, the fight is easy, but random arrows and spears can mess up your rhythm. Take care to avoid all sources of damage.

Some later attacks are avoided with timing and speed, as you need to keep dodging arrows. Old patterns can also resurface with a twist. Keep calm, and you’ll be safe.

When you reach the later stages, you can afford to heal if you’re hurt. Undyne’s last attacks are very similar to her earlier ones, mostly with changes to trip you up.

The further you progress in the fight, the more Undyne speeds up. That’s where the Sea Tea comes in, as you’ll need the SPEED stats to avoid her maniacal attacks. Standing still isn’t a good idea, as she can hurt you if you don’t move.

Eventually, after dealing enough damage to her, Undyne will die, and you can go on your merry way of slaughter and bloodshed. Of course, this is assuming you’re doing a Genocide Run.

Pacifist Run

Pacifist Runs are the complete opposite of Genocide Runs. Instead of killing everything you see, you must take great care to avoid taking lives. You’ll end up fighting Undyne later on, but don’t be afraid. You can spare her even if the method isn’t apparent.

Undyne initially immobilizes you, and you have to deflect her projectiles. After some rounds of this with increasing speeds, you can move. She’ll keep attacking with spears, so make sure you avoid the attacks.

Persevere until you can move, and once you have an opportunity, keep running into the cave to flee. She’ll try to catch up, but eventually, she’ll get too exhausted and drop to the ground.

The Hotlands area where she becomes exhausted has a water cooler. If you give her water from the cooler, you spare her and keep your Pacifist Run intact. However, you must be quick to hand her a cup.

Kill Her or Spare Her?

Depending on your Run, you can either kill or spare Undyne. Sparing her lets you visit her house and even enjoy a cooking lesson. A few different routes can change what happens, but we’ll leave them for you to discover.

Did you kill or spare Undyne the first time you fought her? How many times did it take for you to kill her? Let us know in the comments section below.


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