The answer is  "yes".  A joint tenancy is a type of ownership of real (or personal) property by two or more persons in which each owns an undivided interest in the whole. In order to sell the property as a whole, all joint tenants would need to agree.  That having been said, one joint tenant may sell their interest in the property (not the entire property) without the other joint tenant's permission.  However, they would need to find a buyer who is willing to share the use and possession of the property with the other tenant.  If a joint tenant's interest is sold, the new owner and exisiting owner would become "tenants in common".