Mr. Jones and him are very good friends. Is it I or he?
It could be either I or he. Both would be grammatically correct.
It is he. It is also I, depending on who you are speaking of. If it is yourself and Mr. Jones, it would be I. If it were Mr. Jones and someone else, it would be he. He and Mr. Jones might even be better.
In this case, "he" is the correct choice. The correct sentence would be: "Mr. Jones and he are very good friends."
To determine whether to use "I" or "he" in your sentence, you can try rephrasing the sentence and seeing which pronoun sounds correct.
In this case, you can rephrase the sentence to "Mr. Jones and I are very good friends." and "Mr. Jones and he are very good friends." By removing "Mr. Jones" from the sentence, you get "I am very good friends" and "he is very good friends."
Since "I am" is the correct subject-verb combination, you should use "I" in the sentence: "Mr. Jones and I are very good friends."