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

Yes.

The meaning, spelling, and grammar of "antiga" are identical in both Brazilian and European Portuguese. The only difference lies in pronunciation. In Brazilian Portuguese, the final unstressed "a" is typically pronounced clearly and openly. In European Portuguese, unstressed vowels are often reduced or "swallowed," making the final "a" sound very short, almost like a faint schwa or nearly silent.

Brazilian Portuguese

1. Essa música é muito antiga. (This song is very old.)
2. Ela é uma amiga antiga. (She is an old friend.)
3. Minha antiga casa era perto daqui. (My old house was near here.)
4. Essa roupa é bem antiga. (This clothing is quite old.)
5. Ela é uma funcionária antiga da empresa. (She is a long-time employee of the company.)

European Portuguese

1. Esta música é bastante antiga. (This song is quite old.)
2. Ela é uma antiga amiga. (She is an old friend.)
3. A minha antiga casa era perto daqui. (My old house was near here.)
4. Esta peça de roupa é muito antiga. (This piece of clothing is very old.)
5. É uma antiga funcionária da empresa. (She is a long-time employee of the company.)