simple grammar question

Hello!

Please have a glance at the following sentence

"Jan Kowalski is a person whom I've worked with for a couple of years for the same company"

and tell me, is it grammaticaly correct?

thanks for response

You have definitely used "whom" correctly and the sentence makes grammatical sense. However, the "for the same company" at the end is a little awkward. I would write:

"Jan Kowalsky has been my colleague for the past few years"

The word colleague will indicate that you worked alongside of her - that is, that she is your peer. If you are her boss, then you might write,

"Jan Kowalsky has worked for me for the past few years"

Using "whom" at all is pretentious and should be avoided. Use "who" instead.

What Mary said. :-)

Thanks you both for the answers, I should have explained myself more in details :)

The point is indeed whether I should use 'who' or 'whom' in that sentence.
The sentence has been taken from a formal letter, is 'whom' still pretentious for such purpose?

Thanks Mary for your suggestions

<<The sentence has been taken from a formal letter, is 'whom' still pretentious for such purpose?>>

No. In writing it may be appropriate, but in speech you'd often be called pretentious for using it.

>> "Jan Kowalski is a person whom I've worked with for a couple of years for the same company" <<

It sure is awkward sounding.

It should be:
"Jan K. is a person with whom I have worked."

or:
"I worked with Jan K. for a couple of years at X company. He is a wonderful fellow, etc."

Putting in "for the same company" is awfully redundant, ne?