The supermarket is initially rolling out its Easy Entertaining service in London. It will deliver party food to London addresses from its four dotcom stores in Enfield, Greenford, Aylesford and Croydon.
M&S already offers an online party food service, which allows customers to order food on its website and choose a collection time at a local store.
Tesco claims its new service can cater for events of all sizes and has designed the website with categories including desserts and cakes, buffet foods and party accessories.
Customers will be able to choose a delivery slot with its Delivery Saver customers able to receive the order at no extra delivery cost.
Ken Towle, internet retailing director at Tesco, said the aim of the scheme is to make party planning simpler by offering customers "great party food at our usual low prices, delivered straight to their door."
The launch of the service comes shortly after Tesco launched a Commuter Zone on its website, which enables London commuters to order food on their commute via a mobile-optimised website.