How to tell them apart
際（に） marks a specific moment or opportunity and often carries a sense of taking advantage of that moment, while に当たって/当たり frames an action as a significant event that warrants special preparation or consideration. 際（に） can attach to nouns like この際 or verbs in past tense, whereas に当たって typically attaches to dictionary-form verbs and emphasizes the formality of a milestone. Swapping them for casual moments sounds unnatural: この際、言っておく works, but これに当たって言っておく feels overly stiff.
- 際（に） Use 際（に） for a specific occasion or opportunity, especially when taking action at that moment.
- に当たって/当たり Use に当たって/当たり for formal milestones or significant events that involve preparation or special attention.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| 際（に） ni | at the time of, on the occasion of (formal usage) | N3 |
| に当たって/当たり ni tatte tari | at the time of a particular event or occasion | N2 |
際（に） ni
at the time of, on the occasion of (formal usage)
際（に）means 'when' or 'on the occasion of' and is used in formal, written, or official contexts. It attaches to plain-form verbs or to nouns with の, as in 出火の際. It can also appear as この際 to mean 'at this point, once and for all'.
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出火の際は、すぐに１１９番に電話しなければならない。
In case of fire, you should dial 119 immediately.
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海外へ旅行する際には、通常、パスポートが必要である。
When you travel abroad, you usually need a passport.
に当たって/当たり ni tatte tari
at the time of a particular event or occasion
に当たって/当たり marks a special occasion or event at which something is done, meaning 'on the occasion of'. It follows a noun, as in めでたいときに当たり. The 当たり version is slightly more formal and common in written or ceremonial contexts.
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眠気覚ましにコーヒー飲んで、外の風に当たってくるよ。
To keep myself awake I drink coffee and expose myself to the wind.
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サッカーをしていて後頭部にボールが当たりました。
A ball hit the back of my head while I was playing soccer.
際（に） and に当たって/当たり are JLPT N3–N2 grammar points that Japanese learners often mix up. This page compares them side by side on meanings, usage and example sentences, so you can tell them apart.