How to Say ‘I Don’t Know’ in Korean

Last Updated on May 5, 2021 by 90 Day Korean
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We all like to know the answer to questions. It makes us feel helpful, knowledgeable, and in control.

However, there will always be times when we don’t know the answer to something. In those cases, it’s best to tell the truth and say, “I don’t know”. The other person will respect your honesty!

Today, we will explain how to say “I don’t know” in Korean. We’ve also included a FREE PDF guide to this lesson that you can take with you on the go. Check it out below:

On your marks, get set, go!

Asian businesswomen shrugging her shoulders

How to Say I DON'T KNOW in Korean | 90 Day Korean

Root Verb for ‘I Don’t Know’

There are two verbs we’re going to compare today. They are opposites: One is quite knowledgeable, and one is a bit ignorant.

Ready to meet them?

The first verb is our knowledgeable friend 알다 (alda), which means ‘to know‘. The second verb is our bumbling buddy, 모르다 (moreuda), which means ‘to not know’.

Although we always like to look on the bright side, we’re going to mostly be focusing on 모르다 (moreuda). However, it’s always good to know about the existence of 모르다 (moreuda)’s smarty-pants counterpart!

Let’s get better acquainted with 모르다 (moreuda).

Formal ‘I Don’t Know’ in Korean

Now we know the verbs that we need to use, we can look at how these verbs are conjugated depending on the level of formality that we are using. We will start with the most formal:

1. 잘 모르겠습니다 (jal moreugetseumnida)How to Say I Don’t Know in Korean formal

2. 잘 모릅니다 (jal moreumnida)

These two expressions use the formal ending -ㅂ니다 (-ㅂ nida). This usually is used when speaking to an unknown audience or if you are required to be very formal.

The two above expressions are interchangeable. The 겠 (get) part of the first expression appears in lots of phrases. It shows that the speaker is intending to do something or is making some kind of assumption. It also appears in some fixed expressions, especially related to the verbs ‘to know’ and ‘to not know’.

잘 (jal) means ‘well’, so effectively you are saying ‘I don’t know well’.

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Standard ‘I Don’t Know’ in Korean

1. 몰라요 (mollayo)

2. 잘 몰라요 (jal mollayo)

3. 잘 모르겠어요 (jal moreugesseoyo)How to Say I Don’t Know in Korean standard

모르다 (moreuda) is an irregular verb of the ‘르 (reu)’ variety.

Other verbs and adjectives that follow this pattern include 빠르다 (ppareuda | to be fast), 다르다 (dareuda | to be different), 부르다 (bureuda | to call), and 마르다 (mareuda | to be dry) among others. When conjugating such a verb, an extra ㄹ appears in the word and the “ㅡ” changes to either “ㅏ” or “ㅓ” depending on the vowel in front of it.

You can use the three regular ways of saying ‘I don’t know’ in Korean interchangeably. However, the ‘잘 (jal)’ sounds a little bit more polite. Usually this verb is used to answer questions that include either 알다 (alda) or 모르다 (moreuda) in them.


A: 김 선생님 알아요? (gim seonsaengnim arayo)

Do you know Mr. Kim?

B: 몰라요. (mollayo)

No, I don’t.

You don’t have to say ‘no’ in your answer. It is already implied by the verb ‘I don’t know’.

Informal ‘I Don’t Know’ in Korean

1. 몰라 (molla)How to Say I Don’t Know in Korean informal

2. 모르겠어 (moreugesseo)

When speaking with close friends, you’ll often use informal Korean. It’s more comfortable, simpler, and helps you develop a closer relationship with the other speaker.

When saying the informal version of ‘I don’t know’, this is the same as the standard Korean form but without the ‘요 (yo)’.

Hopefully this lesson has given you a better understanding of how to say ‘I don’t know’ in Korean.

Soon you’ll be turning 몰라요 (mollayo) into 알아요 (arayo)!

We’ve got more great Korean Phrases for you to learn. So what are you waiting for?

    20 replies to "How to Say ‘I Don’t Know’ in Korean"

    • Avatar for Daniel Daniel

      Is it okay to say “mollayo hangul” for “i don’t know korean”

      • Avatar for 90 Day Korean 90 Day Korean

        Hi, Daniel! It would be better to say “한국말 몰라요” [Hangungmal mollayo] to say “I don’t know Korean”. ^^

    • Avatar for Jaya Jaya

      Is this another way of saying it? 나는 모른다

    • Avatar for Maya Maya

      This helped me so much, I always thought the only meaning for ‘I don’t know’ is moreugesso. Thanks a bunch.

    • Avatar for Holly Holly

      This was so helpful! I recently watched a video in Korean and I thought that it was spelt with ㅂ instead ㅁ. It makes so much more sense!

    • Avatar for Sabrina Sabrina

      어떤 문장을 더 자연스러워요?
      – 이 노래를 몰랐어요.
      – 이 노래를 알지 못했어요.

      • Avatar for 90 Day Korean 90 Day Korean

        Hi Sabrina! 어떤 문장”이” 더 자연스러운지 알려줄게요 (Let me tell you which sentence sounds more natural!)
        They’re both good sentences, but 이 노래를 몰랐어요 might be more often used in daily life. ^^

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