Avoir besoin de can be followed by either a noun (its most typical pattern) or an infinitive verb. Both are fully correct and standard French.

1. With a noun (most common)

This is the pattern learners know first.

Examples:

• J’ai besoin de temps.
  “I need time.”
• Elle a besoin d’aide.
  “She needs help.”
• Nous avons besoin de ton avis.
  “We need your opinion.”

2. With an infinitive verb (equally correct)

French allows avoir besoin de + infinitive to express a necessity related to performing an action. This structure is widely used in everyday speech and writing.

Examples:

• J’ai besoin de dormir.
  “I need to sleep.”
• Elle a besoin de se reposer.
  “She needs to rest.”
• Ils ont besoin de travailler davantage.
  “They need to work more.”
• Tu as besoin d’étudier pour réussir.
  “You need to study in order to succeed.”

This use is not marginal. It appears in all major grammars and dictionaries and is extremely common in real usage.

3. Why learners sometimes think it must take a noun

Two reasons:

1. Early teaching often introduces the noun pattern first and delays infinitives.
2. The infinitive verb following de can look like a noun grammatically, because infinitive verbs behave like verbal nouns in French.

But from the perspective of native speakers, both structures are absolutely natural.

4. Cases where only a noun works

If you want to say that you need something rather than the action of doing something, the noun is the only option:

• J’ai besoin d’un café.
• J’ai besoin d’un médecin.

You cannot replace those with an infinitive.

5. Comparison with English

Avoir besoin de + infinitive matches English “to need to + verb,” while the noun version matches “to need + noun.”

So:

• J’ai besoin de dormir → “I need to sleep.”
• J’ai besoin de sommeil → “I need sleep.”

Summary

• Avoir besoin de + noun is standard and frequent.
• Avoir besoin de + infinitive is also fully correct and expresses needing to perform an action.
• Both patterns are equally legitimate in French grammar and in actual usage.