The fans marched through Italy’s financial capital, setting off paper bombs and smashing beer bottles in Milan’s Piazzale Cadorna, Tgcom24 reported.
The 400-strong crowd then headed to nearby Piazza Castello, chanting and setting off firecrackers as they went.
Extra metro trains had been arranged to ferry the fans to San Siro stadium, where French side St Etienne was due to lock horns with Inter Milan.
But the metro line temporarily came to a halt as drunk French fans argued and set off a firecracker inside one of the carriages.
The football supporters then joined around 10,000 French fans to see their side draw 0-0 against Inter.
St Etienne fans have been involved in violence before and were banned from attending away games last year after they attacked supporters of Nice.
Watch a video of the French fans in Milan: