Yes, a contract to lease is legally binding in Delaware. When both parties sign the written lease document, it becomes legally binding. However, this is not the only way that a lease can become binding in Delaware.
If the landlord does not sign the lease but accepts a rent payment from the tenant, it has the same effect as signing the lease. Likewise, if a tenant does not sign the lease but moves onto the property and pays rent, it has the same effect as signing the lease. If a lease becomes validated in this way, it is only in effect for one year (25 DE Code § 5110 (2019)). This is referred to as a ‘tendered lease’.
The information for this answer was found on our Delaware Residential Lease Agreement answers.