Under the one-year deal the retailer' name will be displayed on United's home and away strips.
Stephen Thompson, marketing director of Morning Noon & Night and a director of Dundee United said: "Morning Noon & Night has proved to be the perfect vehicle for United sponsorship as we are looking for ways to increase our profile throughout Scotland.
"This sponsorship ensures that we will be on television and in the national press. It is a great deal for everyone concerned."
The chain is owned by United chairman Eddie Thompson.