N2 Reasons, Causes, and Expectations

~のことだから: meaning, usage and examples

~のことだから means: knowing... / since it's...

Updated 9 November 2026 · By the My Senpai team · Spotted a mistake? Tell us

Examples

1. 彼かれのことだから、きっと遅刻ちこくするだろう。

   Knowing him, he'll probably be late.

2. 田中たなかさんのことだから、必かならず成功せいこうするよ。

   Knowing Mr. Tanaka, he's sure to succeed.

3. 鈴木すずきさんのことだから、もう準備じゅんびはできているだろう。

   Knowing Ms. Suzuki, she has probably finished preparing already.

4. あの店みせのことだから、週末しゅうまつはきっと行列ぎょうれつができている。

   Knowing that restaurant, there's sure to be a line on the weekend.

When to use it

のことだから means "knowing (someone)": the speaker uses what they know about a person's character or habits to predict what that person will do, as in 鈴木すずきさんのことだから、もう準備じゅんびはできているだろう. The prediction can be good or bad, and it rests on what the speaker knows about the person, not on evidence seen right now.

Nuance

Conversational and common in speech, also fine in writing. The second clause is a guess, so it usually ends with だろう, に違ちがいない, きっと, or はずだ. The noun is usually someone both speakers know well, not a stranger.

Compare

からには means "now that" and leads to determination (約束やくそくしたからには守まもる). さすが praises a result that matches a reputation (さすがプロだ). ところをみると guesses from something seen right now. のことだから predicts behavior from personality: 彼かれのことだから、また忘わすれるだろう.

Tip: Think of it as "Knowing X..." in English. If your sentence does not end in a guess, the pattern probably does not fit.