No fiarse un pelo

not to trust someone one bit; **not to trust someone one bit**; **not to trust someone at all**; **not to trust someone an inch**; **to have absolutely no confidence in someone**; **to be very suspicious of someone**

No fiarse un pelo means not to trust someone or something at all, not to trust someone one bit, or to be extremely suspicious.

The expression emphasises a complete lack of trust.

A common construction is:

No me fío un pelo de él.

→ I don't trust him one bit.

• completely distrusts another person
• suspects that someone is dishonest
• doubts someone's intentions
• believes that a situation is risky or unreliable
• has serious reservations about something

The expression uses pelo as a metaphor for a very small quantity.

Spanish frequently uses un pelo to mean a tiny amount:

Falta un pelo.

→ It's just a tiny bit short.

Por un pelo.

→ By a hair / by the narrowest margin.

In no fiarse un pelo, the tiny quantity is applied to trust: the speaker does not have even the smallest amount of confidence in the person or thing concerned.

The expression is stronger than simply saying:

No me fío de él.

→ I don't trust him.

Adding un pelo intensifies the statement:

No me fío un pelo de él.

→ I don't trust him one bit.

It is therefore useful when the speaker wants to emphasise complete distrust.

Spanish uses very small physical quantities to intensify expressions surprisingly often:

• No fiarse un pelo → not trust one bit.
• No importar un bledo → not care one bit.
• No importar un comino → not care one bit.
• No valer un pimiento → not be worth much.
• Faltar un pelo → fall short by a tiny amount.

In all of them, the tiny quantity serves to emphasise the extreme degree of the statement.

Do not translate:

No me fío un pelo de él.

as:

I don't trust a hair of him.

Natural translations include:

I don't trust him one bit.

I don't trust him at all.

I wouldn't trust him as far as I could throw him.

The last is more emphatic and colloquial than the Spanish original.