Has there ever been a 6–5 in the Serie A?

Yes, 2 times.

The first time: November 15, 1942, Genova 1893 beat Lazio (Genova 1893 6–5 Lazio).

The last time: November 6, 1949, Internazionale beat AC Milan (Internazionale 6–5 AC Milan), 76 years ago.

Home wins: 2. Away wins: 0.

Nearby scores

1. 7–4 1 time
2. 7–5 Never
3. 7–6 Never
4. 6–4 4 times
5. 6–5 2 times
6. 6–6 Never
7. 5–4 16 times
8. 5–5 1 time

All games

1. November 6, 1949 Internazionale 6–5 AC Milan
2. November 15, 1942 Genova 1893 6–5 Lazio