What is the function of “le” in this sentence?

“Me interesa lo que le pasa a él.”

See a translation

I will start by saying that the «a él» in this sentence is optional, you can remove it.

Me interesa lo que le pasa.

So, short answer:

This sentence in English would be:

I'm interested in what's happening to him.

The «Le» in the Spanish sentence is the indirect object pronoun of «Él», it lets you know who the person is talking about without having to use the pronoun. In other words, «Le» serves as the «To him» in the English sentence.

Lo que LE pasa.
What's happening TO HIM.
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Long answer:


Indirect object pronouns

Yo -> Me
Tú -> Te
Usted / Él / Ella / Eso / Ello -> Le
Nosotros / Nosotras -> Nos
Ustedes / Ellos / Ellas -> Les.

Sentences have direct and indirect objects. Direct objects are the ones affected by the actions of the verb and indirects objects are the ones to whom the action targets.

For example:

Yo LE traigo agua.
I bring HIM water.

Direct obj: Water (the thing being brought)
Indirect obj: Him (The water is for him)


Ella les dijo todo lo que sabía.
She told them everything she knew.

Direct Obj: Everything she knew (that's what she told)
Indirect obj: Them (Who she told that to)


Yo LE cocino el desayuno.
I cook HER breakfast.

Direct obj: Breakfast
Indirect obj: Her


Back to your sentence,

Me interesa lo que le pasa.
I'm interested in what's happening to him.

Direct Obj: Whatever's happening.
Indirect obj: Him ( because whatever's happening is happening to him)