Prepositions after adjectives

Uncertain about vs. uncertain of

Both uncertain about and uncertain of are standard. About is common for topics or decisions, while of often refers to facts, awareness, or confidence.

Quick answer

Which preposition is used with uncertain?

Use uncertain about for topics, plans, or choices. Use uncertain of for facts, details, or whether something is true. Both are idiomatic, but they are used in slightly different contexts.

She is uncertain about her future career.
I am uncertain of the exact date.
They felt uncertain about moving abroad.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

uncertain about + topic

Talking about doubts or indecision

Use uncertain about when discussing plans, opinions, actions, or general situations.

He is uncertain about accepting the offer.

We remain uncertain about the new policy.

uncertain of + fact

Referring to incomplete knowledge

Use uncertain of when someone does not know or cannot confirm a fact or detail.

She was uncertain of his intentions.

I am uncertain of the meeting time.

uncertain whether + clause

Introducing alternatives or possibilities

Whether often follows uncertain before a full clause.

They were uncertain whether the train would arrive on time.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction

Example

Meaning

uncertain about

She is uncertain about the next step.

unsure about a topic, action, or decision

uncertain of

He was uncertain of the answer.

not fully sure of a fact or piece of information

uncertain whether

I am uncertain whether we should continue.

unsure between possibilities

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using of for broad situations

About is usually more natural for decisions or general topics.

✕ She is uncertain of changing jobs. ✓ She is uncertain about changing jobs.

Using about before a clause

Use whether before a full clause.

✕ We are uncertain about the project will continue. ✓ We are uncertain whether the project will continue.

Quick practice

Choose the expression that matches the intended meaning.

1. She is uncertain ___ the final result.

2. They felt uncertain ___ moving to another country.

3. I am uncertain ___ we have enough time.

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Frequently asked questions

Is uncertain about more common than uncertain of?

Uncertain about is especially common for decisions and situations, while uncertain of is often used for facts or knowledge.

Can I say uncertain on?

Uncertain on appears in some informal contexts, especially with topics, but uncertain about is more standard.

Can uncertain be followed by a clause?

Yes. Uncertain whether and uncertain if can introduce clauses.

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