Can You Get Both Fossils in Pokemon FireRed?

No. In Pokemon FireRed, you can only choose one fossil in Mt. Moon, and the other is permanently taken away in that playthrough.

Once you select either the Helix Fossil or the Dome Fossil, the unchosen fossil is removed immediately.

There is no option to collect both in the same save file.

The same rule applies in Pokemon LeafGreen.

Why This Choice Feels Risky#

The fossil decision happens early in the game, before most players fully understand its long-term impact and is one of the choices and decisions in Pokemon FireRed that cannot be reversed.

The game does not clearly explain what each fossil becomes.
There is no warning that the other fossil will disappear.
The choice cannot be reversed without restarting.

For players who care about completion or avoiding permanent loss, this moment can create hesitation.

What Actually Happens#

After defeating Team Rocket in Mt. Moon:

You are asked to choose one fossil.
The other fossil is immediately taken away.
The unchosen fossil does not reappear later in the game.

There is no later opportunity in Pokemon FireRed to obtain the remaining fossil within the same playthrough.

Other rewards in FireRed follow a similar one-time choice structure, such as choosing between Hitmonlee and Hitmonchan.

The rival takes the remaining fossil after the player chooses one in Pokémon FireRed.

In Short#

You must choose between the Helix Fossil and the Dome Fossil.

The decision is permanent for that playthrough.

It does not affect story completion, but you cannot collect both in a single save file.