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

Yes

The word "concordo" is identical in meaning, grammar, and spelling in both Brazilian and Continental Portuguese. The only difference lies in pronunciation. In Brazil, the vowels tend to be more open and the rhythm of the word is more melodic and "stretched." In Portugal, vowels—especially unstressed ones—are much more closed and reduced, often making the word sound shorter and more "clipped" to a Brazilian ear.

Brazilian Portuguese Examples

1. Eu concordo totalmente com você. (I totally agree with you.)
2. Concordo, acho que essa é a melhor ideia. (I agree, I think this is the best idea.)
3. Não concordo com o que ele disse agora há pouco. (I don't agree with what he said a little while ago.)
4. A gente concorda que o filme foi muito bom. (We agree that the movie was very good.)
5. Concordo plenamente com o seu ponto de vista. (I completely agree with your point of view.)

Continental Portuguese Examples

1. Estou de acordo com o que disseste. (I agree with what you said.)
2. Concordo contigo, a ideia é excelente. (I agree with you, the idea is excellent.)
3. Não estou de acordo com essa decisão. (I don't agree with this decision.)
4. Concordo plenamente com a tua opinião. (I completely agree with your opinion.)
5. Estou de acordo com o que foi decidido na reunião. (I agree with what was decided in the meeting.)