Is the word agradeci the same in Brazilian and European Portuguese?

Yes

The word agradeci is the first-person singular past tense (pretérito perfeito) of the verb agradecer (to thank). Its spelling, grammatical function, and meaning are identical in both Brazilian and Continental Portuguese. The only difference lies in pronunciation: in Brazil, vowels tend to be more open and the word is articulated with more phonetic clarity, whereas in Portugal, unstressed vowels are often more reduced or "swallowed," leading to a more closed and clipped sound.

Brazilian Portuguese Examples

1. Eu agradeci ao professor pela nota. (I thanked the teacher for the grade.)
2. Agradeci muito a ajuda que você me deu. (I thanked you very much for the help you gave me.)
3. Agradeci o presente que ganhei de aniversário. (I thanked [them] for the gift I got for my/my birthday.)
4. Eu agradeci ao garçom pela comida. (I thanked the waiter for the food.)
5. Agradeci a oportunidade de trabalhar aqui. (I thanked [them] for the opportunity to work here.)

Continental Portuguese Examples

1. Eu agradeci ao professor pela nota. (I thanked the teacher for the grade.)
2. Agradeci imenso a ajuda que me deste. (I thanked you immensely for the help you gave me.)
3. Agradeci o presente que recebi de aniversário. (I thanked [them] for the gift I received for my birthday.)
4. Eu agradeci ao empregado de mesa pela comida. (I thanked the waiter for the food.)
5. Agradeci a oportunidade de trabalhar aqui. (I thanked [them] for the opportunity to work here.)