Can You Get More Than One Eevee in Pokemon FireRed?

No. You only receive one Eevee directly in Pokemon FireRed.

However, additional Eevee can still be obtained later through breeding.

Once you evolve Eevee using an Evolution Stone, you cannot return it to its base form in that save file.

The same rules apply in Pokemon LeafGreen.

Why This Moment Feels Uncertain#

Eevee has multiple evolution paths and is obtained through one of the limited rewards and single-source Pokemon in Pokemon FireRed that only occur once during a playthrough.

In Pokemon FireRed, Eevee can evolve into:

No other evolutions are available in this version.

Using a Water Stone, Thunder Stone, or Fire Stone permanently changes it.

The game does not clearly warn that this decision cannot be undone.
For many players, this raises a concern:

If I evolve Eevee now, will I lose access to the other forms forever?

In Pokemon FireRed:

However:

The game includes a breeding system later in the playthrough.
Even if Eevee has already evolved, you can still produce Eevee through breeding.
Gender does not create a permanent restriction because Ditto can be used.

This means you start with a single Eevee source, but you are not permanently limited to only one total Eevee.

Other gift Pokémon in FireRed follow a similar structure, such as the single Lapras received in Silph Co.

Eevee received at Celadon Mansion in Pokemon FireRed.

You only receive one Eevee directly in Pokemon FireRed.

Its evolution is permanent.

Only Vaporeon, Jolteon, and Flareon are available in this version.

You can still obtain more Eevee later through breeding, but the original evolution choice itself cannot be undone.