Les actes parlent plus que les mots.
This is a literal translation that captures the essence of the proverb.
Here are some other options, with slight nuances:
* Ce sont les actes qui comptent. (Actions are what matters.)
* Les paroles s'envolent, les écrits restent. (Words fly away, writings remain.) - This is a different proverb but conveys a similar sentiment.
* L'action est plus éloquente que la parole. (Action is more eloquent than speech.)
* Il vaut mieux faire que dire. (It's better to do than say.)
The best translation will depend on the context and the desired tone.