Explanation

Quick Answer

Spanish direct object pronouns (pronombres de objeto directo), such as lo, and Spanish indirect object pronouns (pronombres de objeto indirecto), such as le, are used in place of nominal direct and indirect objects.

There are a few important rules that must be followed when using direct object pronouns and indirect object pronouns together.

But first, let's review Spanish direct and indirect object pronoun forms!

Spanish Direct Object Pronoun and Indirect Object Pronoun Forms

Direct Object Pronoun	Indirect Object Pronoun	English
me	me	me
te	te	you
lo, la	le	him, her, it, you
nos	nos	us
os	os	you (all)
los, las	les	them, you (all)

And now for the rules!

Maintaining Order

When direct and indirect object pronouns are used together in a sentence, the indirect object pronoun comes before the direct object pronoun.

examples
Marcos nos trajo la comida a nosotros. Marcos brought the food to us.
Marcos nos la trajo. Marcos brought it to us.
Mi madre está comprándome una pizza. My mom is buying me a pizza.
Mi madre está comprándomela. My mom is buying it for me.
Dame el control remoto. Give me the remote control.
Dámelo. Give it to me.
No quiero decirte la verdad. I don’t want to tell you the truth.
No quiero decírtela. I don’t want to tell it to you.

Notice that when object pronouns are attached to a verb, it's often necessary to add an accent in order to preserve the natural stress of the verb.

Changing Le to Se

The indirect object pronouns le and les change to se when followed by the direct object pronouns lo, la, los and las.

le/les -> se before lo, la, los, las

examples
Le digo el cuento a María. I tell the story to María.
Se lo digo. I tell it to her.
Mi abuelo les compró los regalos a los niños. My grandfather bought gifts for the children.
Mi abuelo se los compró. My grandfather bought them for them.

Negatives

When a sentence with object pronouns is negative, the negative word (for example, noor nunca directly precedes any object pronouns.

examples
No te la tengo. I don’t have it for you.
Ella nunca compra helado para sus hijos. Ella nunca se lo compra. She never buys ice cream for her kids. She never buys it for them.