No. A helium balloon floats on Earth because it displaces surrounding air that is heavier than the helium inside. The Moon has virtually no atmosphere, so there is almost no surrounding gas to provide enough buoyant lift.
Why helium balloons rise on Earth
A balloon displaces a volume of air. If the weight of that displaced air exceeds the combined weight of the helium, balloon material and string, the balloon has net upward buoyant force. Helium itself is not a magical anti-gravity substance; it simply weighs less than the same volume of ordinary air under comparable conditions.
The Moon has almost no air to displace
The lunar environment has only an extremely thin exosphere. A party balloon cannot push aside enough surrounding gas to create Earth-like buoyant lift. It would still experience lunar gravity, although that gravity is weaker than Earth’s. Less weight is not the same as having enough lift to float.
The balloon might also behave very differently
A balloon filled at Earth pressure and taken into near-vacuum faces a large pressure difference between its inside and outside. It may expand considerably or rupture, depending on its material and inflation. A real lunar demonstration would also require dealing with temperature swings and vacuum exposure. The images here are conceptual, not photographs of a real lunar test.
How this differs from the basketball question
A basketball bounces by exchanging energy with a surface, while a helium balloon floats by displacing surrounding gas. Weak lunar gravity affects both objects’ weight, but the near-absence of atmospheric gas matters especially for the balloon.
Frequently asked questions
Would a heavier balloon float on the Moon?
No ordinary party balloon would float through buoyancy without a sufficiently dense surrounding fluid.
Would it float in a pressurized Moon habitat?
Potentially, yes. If the habitat contained Earth-like air and the balloon had appropriate helium and materials, it could experience familiar buoyancy.
Related reading: Would a basketball bounce higher on the Moon?.
Sources and further reading: NASA: Moon atmosphere; NASA: Moon gravity.
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