Felicidades por el trabajo.

In Spanish, felicidades is a fixed expression that means congratulations. It is normally used in the plural, even when English might not make you think of it that way.

So:

• Felicidades = Congratulations
• not usually felicidad for this meaning

A related word is felicitaciones, which also means congratulations and is very common in many parts of Latin America.

Por is used here to mean for in the sense of because of, on account of, or for this achievement/reason.

So:

• Felicidades por el trabajo = Congratulations for/on the work/job

This is the normal pattern:

• Felicidades por tu logro = Congratulations on your achievement
• Felicidades por el ascenso = Congratulations on the promotion
• Gracias por tu ayuda = Thanks for your help

A learner might want to use para, but para would not sound natural here.

Spanish often uses the definite article more than English does.

Here, el trabajo usually refers to a specific job/work that both people understand from context. For example:

• the job someone got
• the work someone did
• the project or task being talked about

Without the article, Felicidades por trabajo would sound incorrect.

You could also hear:

• Felicidades por tu trabajo = Congratulations on your work
• Felicidades por el nuevo trabajo = Congratulations on the new job

It can mean either, depending on context.

• trabajo = work
• trabajo = job

So this sentence could refer to:

• congratulating someone on a job well done
• congratulating someone for getting a job

If you want to be more specific, Spanish often adds more detail:

• Felicidades por el nuevo trabajo = Congratulations on the new job
• Felicidades por tu trabajo = Congratulations on your work
• Buen trabajo = Good job

Not always. It depends on the situation.

If you mean Good job!, Spanish more often uses:

• ¡Buen trabajo!
• ¡Muy buen trabajo!
• ¡Excelente trabajo!

Felicidades por el trabajo sounds more like Congratulations on the work/job, which can feel a little more formal or tied to an achievement.

So:

• for praise after performance: ¡Buen trabajo!
• for congratulating someone on an accomplishment or job: ¡Felicidades por el trabajo!

Yes. In much of Latin America, felicitaciones is very common and completely natural.

So these are both good:

• Felicidades por el trabajo
• Felicitaciones por el trabajo

In some regions, one may sound more common than the other, but both are standard and widely understood.

Sometimes, yes.

• por el trabajo = for the job/work, often referring to something specific already understood
• por tu trabajo = for your work, which sounds more directly personal

Compare:

• Felicidades por el trabajo = Congratulations on the job/work
• Felicidades por tu trabajo = Congratulations on your work

If you are speaking directly to someone about something they did, tu trabajo can sound warmer and clearer.

If you are writing it as an exclamation, standard Spanish punctuation uses both opening and closing exclamation marks:

• ¡Felicidades por el trabajo!

In casual texting or informal writing, people sometimes leave them out, but the fully correct written form is with both marks.

A simple pronunciation guide is:

feh-lee-see-DAH-des por el trah-BAH-ho

A few helpful notes:

• c in felicidades sounds like s in Latin America
• j in trabajo sounds like a strong English h
• the stress is on:
  • da in felicidades
  • ba in trabajo

So the rhythm is:

• fe-li-ci-DA-des
• tra-BA-jo

Yes. It works in both.

It is polite and neutral enough for:

• a friend
• a coworker
• a classmate
• a professional message

If you want it to sound more formal, you might expand it a little:

• Muchas felicidades por el trabajo.
• Felicitaciones por el trabajo realizado.

If you want it to sound more casual:

• ¡Buen trabajo!
• ¡Felicidades!