The Mexican Football Federation has been fined 10,000 Swiss francs (£7,615) after its fans sang homophobic chants.
The chants came during Mexico's World Cup win over Germany on Sunday.
Football's world governing body Fifa said it had also warned Mexico's federation, the FMF, it could face "additional sanctions" if there are "repeated infringements" - though a similar warning was made in November.
"Fifa has a zero-tolerance approach to discrimination," a spokesperson said.
A Fifa disciplinary panel has also sanctioned the Serbian Football Association with a 10,000 Swiss franc fine for the "display of an offensive and political banner by Serbian fans" during their match against Costa Rica.
The FMF has repeatedly asked Mexican fans to refrain from using the chant, which features the Spanish word for a male prostitute.
It is usually sung when the opposition goalkeeper is taking a goal kick.
Last year the FMF successfully appealed to the Court of Arbitration for Sport (Cas) against two larger Fifa fines for the same offence.
Cas agreed that the chant was not intended to "offend or discriminate" and downgraded the fines to a warning.
However, it also said the chant could still be "considered discriminatory or insulting and should not be tolerated in football stadiums".
It said should the offence take place in the future, "harsher sanctions" should be imposed.