A sublease agreement is a legal document that allows a tenant to sublet a property to someone else (subtenant). Also known as subletting.A sublease agreement is a rental contract used for rerenting a currently leased unit to a new tenant. A sublease agreement is a form that allows a tenant to rent space they have under a written contract with a landlord to someone else. A Sublease Agreement is a contract that outlines the terms of a sublease between an existing tenant and a subtenant. Set out fair and legally binding terms as you lease your Ontario premises. Cover crucial aspects with our Sublease Agreement Sample Ontario template.