No, residential lease agreements do not need to be notarized in Iowa. Leases for other types of property may need to be notarized, such as farm leases, but residential leases do not.
The tenant and landlord can agree to notarize the lease if they wish, but it is not required by Iowa state law. As long as the lease meets the criteria to be legally binding, it is not necessary.
The information for this answer was found on our Iowa Residential Lease Agreement answers.