Preposition after adjective

suspicious of, about, to, in or by?

Suspicious is most commonly followed by of for distrust and about for concern or doubt. Other prepositions usually belong to different sentence structures.

Quick answer

Which preposition is used with suspicious?

Use suspicious of a person, action, or situation when you do not trust it. Use suspicious about when you are uneasy or doubtful about something. Suspicious to, suspicious in, and suspicious by are not standard complements after the adjective.

I'm suspicious of his explanation.
She became suspicious about the sudden changes.
Police were suspicious of the account from the start.

Choose the pattern by meaning

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

suspicious of + person/thing

Distrusting someone or something

Use of after suspicious to express distrust or belief that something is wrong.

They were suspicious of the new supplier.

He sounded suspicious of her motives.

suspicious about + situation

Feeling doubtful or uneasy

About is used for concerns or uncertainty about a situation or detail.

I'm suspicious about the timing.

Voters grew suspicious about the promise.

be suspicious when + clause

Describing a reaction

A clause often follows suspicious to explain the reason for doubt.

I get suspicious when people avoid details.

She became suspicious when the files disappeared.

See the difference in context

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

Construction

Example

Meaning

suspicious of

We are suspicious of the offer.

Standard pattern for distrust or doubt.

suspicious about

He felt suspicious about the sudden delay.

Used for concern or uncertainty about a situation.

suspicious to

The message looked suspicious to the security team.

To introduces the person who finds something suspicious; it is not the complement after suspicious.

suspicious in

The auditors noticed suspicious activity in the accounts.

In introduces location or context, not a complement of suspicious.

suspicious by

She was recognised by her accent.

Suspicious by is not an idiomatic adjective pattern.

Common mistakes

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

Using suspicious by

Use of or about after suspicious.

✕ They were suspicious by his behaviour. ✓ They were suspicious of his behaviour.

Confusing suspicious to

To can identify the observer, not the thing doubted.

✕ I am suspicious to the plan. ✓ I am suspicious of the plan.

Overusing about

Of is usually stronger and more direct for distrust of a person or thing.

✕ She is suspicious about him. ✓ She is suspicious of him.

Quick practice

Choose the expression that matches the intended meaning.

1. The manager became suspicious ___ the missing documents.

2. I'm suspicious ___ the sudden price increase.

3. The email looked suspicious ___ the customer.

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Frequently asked questions

What is the difference between suspicious of and suspicious about?

Suspicious of usually expresses distrust of a person or thing. Suspicious about often refers to doubts about a situation or detail.

Can suspicious be followed by a clause?

Yes. You can say suspicious that or suspicious when in natural contexts.

Is suspicious by correct?

No. Suspicious by is not a standard adjective pattern in current English.

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