Actually, neither of these sentences is correct.
"Also" could appear in the sentence in these ways:
1. Also, his friend is coming, isn't he?
2. His friend is also coming, isn't he?
3. His friend is coming also, isn't he?
As you can see, "his friend" is the subject, the singular subject, of these sentences.
With the word order of your sentence, you could use "as well as"; in that case, "he" is the subject. "As well as" and similar expressions do not change the subject, which, in this case, remains singular:
4. He, as well as his friend, is coming.
You could also construct the sentence with a compound subject:
5. Both he and his friend are coming, aren't they.
6. He's coming and his friend is coming, aren't they?
7. He and his friend are both coming, aren't they?
Or, in other ways, with a singular subject:
8. He's coming with his friend, isn't he?
9. His friend is coming with him, isn't he?
10. He's coming together with his friend, isn't he?
11. His friend is coming along with him, isn't he?