prepare (someone) a surprise

Translations
подготовить (кому-то) сюрприз
I decided to prepare him a surprise for his birthday.
Я решил подготовить ему сюрприз на день рождения.
Definitions
To arrange or organize something unexpected for someone, usually to make them happy or excited, without letting them know in advance.
Words
surprise

noun
сюрприз
prepare

verb
готовить