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

Yes

The only differences between the word "isso" in Brazilian Portuguese and Continental Portuguese are phonetic. In Brazilian Portuguese, unstressed vowels (like the "o" in "isso") tend to be more open and clearly articulated. In Continental Portuguese, there is a much stronger tendency toward vowel reduction, meaning the unstressed "o" is often shortened or nearly swallowed, making the word sound more clipped or even consonant-heavy to a Brazilian ear. The meaning, grammar, spelling, and fundamental usage remain identical.

Brazilian Portuguese Examples

1. Isso é muito legal! (That is very cool!)
2. Eu não entendi isso. (I didn't understand that.)
3. Isso aí, pode continuar. (That's it, you can continue.)
4. O que é isso na sua mão? (What is that in your hand?)
5. Isso é muito chato. (That is very annoying/boring.)

Portuguese (Continental) Examples

1. Isso é muito giro! (That is very cool!)
2. Eu não percebi isso. (I didn't understand that.)
3. Isso mesmo, podes continuar. (That's it, you can continue.)
4. O que é isso na tua mão? (What is that in your hand?)
5. Isso é uma seca. (That is a drag/very boring.)