Je suis inquiet(e).
* Je suis means "I am".
* inquiet(e) is the adjective "worried". It changes to "inquiète" for feminine subjects.
Here are some other ways to express worry in French, depending on the context:
* J'ai des soucis. (I have worries)
* Je m'inquiète. (I am concerned)
* Je suis angoissé(e). (I am anxious)
* Je suis stressé(e). (I am stressed)
* J'ai peur. (I am afraid)
The best choice will depend on the intensity of your worry and the specific situation.