Has there ever been a 5–5 in the Liga MX?

Yes, 8 times.

The first time: November 11, 1945, América and Atlante drew (América 5–5 Atlante).

The last time: September 20, 2003, Santos Laguna and Monterrey drew (Santos Laguna 5–5 Monterrey), 23 years ago.

Nearby scores

1. 6–4 17 times
2. 6–5 3 times
3. 6–6 1 time
4. 5–4 24 times
5. 5–5 8 times
6. 4–4 50 times

All games

1. September 20, 2003 Santos Laguna 5–5 Monterrey
2. December 29, 1988 Tampico Madero 5–5 Correcaminos UAT
3. October 12, 1986 Irapuato 5–5 Tecos UAG
4. July 25, 1951 Oro 5–5 Marte
5. April 8, 1948 España 5–5 Veracruz
6. November 7, 1946 Marte 5–5 Oro
7. January 27, 1946 Atlas 5–5 Asturias
8. November 11, 1945 América 5–5 Atlante