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

Yes

The spelling, meaning, and grammatical function of the word are identical in both Brazilian and Continental Portuguese. The only differences are in pronunciation and the surrounding syntax (the way the word is used in a sentence). In Brazilian Portuguese, the nasal diphthong at the end of the word is typically more open and clearly articulated, whereas in Continental Portuguese, the vowel sound is more closed. Additionally, while the word "ninguém" itself does not change, Brazilians commonly use the verb ter (to have) to express the absence of people, while Portuguese people more naturally use the verb haver (to exist/there be).

Brazilian Portuguese Examples:

1. Não vi ninguém na festa. (I didn't see anyone at the party.)
2. Ninguém me ligou ontem. (No one called me yesterday.)
3. Não tem ninguém no escritório agora. (There is no one in the office right now.)
4. Acho que ninguém sabe a verdade. (I think no one knows the truth.)
5. Eu não contei nada para ninguém. (I didn't tell anyone anything.)

Continental Portuguese Examples:

1. Não vi ninguém na festa. (I didn't see anyone at the party.)
2. Ninguém me ligou ontem. (No one called me yesterday.)
3. Não há ninguém no escritório agora. (There is no one in the office right now.)
4. Acho que ninguém sabe a verdade. (I think no one knows the truth.)
5. Não contei nada a ninguém. (I didn't tell anyone anything.)