Valacyclovir is used to treat infections caused by certain types of viruses. In children, it is used to treat cold sores around the mouth (caused by herpes simplex) and chickenpox (caused by varicella zoster). In adults, it is used to treat shingles (caused by herpes zoster) and cold sores around the mouth.

Valacyclovir is also used to treat outbreaks of genital herpes. In people with frequent outbreaks, this medication is used to reduce the number of future episodes.