The German manufacturer saw Lewis Hamilton and George Russell finish second and third at Barcelona behind race winner Max Verstappen, moving the squad up to second in the constructors' championship standings.
But a few hours after the race, the team was notified that team members may have breached the regulations in the post-race parc ferme zone that is created in the pitlane.
The FIA requested that a representative of Mercedes, plus the physios of both Hamilton and Russell, should report to the stewards on Sunday evening.
Teams are regularly notified ahead of the race about who and who is not allowed into the parc ferme area following the race.
There is also a strict limit on when physios are allowed to interact with their drivers ahead of the podium ceremony.
In notes sent to the teams by the FIA on Sunday morning ahead of the Spanish GP, it was said: "Other than the team mechanics (with cooling fans if necessary), officials and FIA pre-approved television crews and FIA approved photographers, no one else will be allowed in the designated area once the cars are in the Parc Ferme area (no team PR personnel.)
The FIA media delegate reported to the stewards that Mercedes physios and driver assistants had entered parc ferme in violation of the post-race interview and podium ceremony.
This was confirmed by video evidence and Mercedes has copped a €10,000 fine as a result.
Furthermore, it added: "Driver physios must wait outside the cool down room behind the podium until the podium ceremony has concluded following the instructions given to all teams by the Media Delegate."
This is not the first time that the issue of driver physios breaching parc ferme regulations has come up.
At last year's Austrian Grand Prix, the top three finishers, Charles Leclerc, Verstappen and Hamilton, were all given suspended 10,000 euro fines for a similar breach of parc ferme rules.
That was because team physios had entered the parc ferme area during the post-race moments, breaching the guidelines sent out earlier that day.
