It was registered with the Flag Institute on 13 December 2018 following its announcement at a reception hosted by the Lord Provost.

[1] This saltire design on blue reflects the local birthplace of the national flag, with the cross in gold signifying the wealth of the county's farmlands and reputation as the granary of Scotland.

Design B The three horizontal bands represent the key industries of the county – blue for the sea and fishing, yellow for the beaches and tourism, and green for the farming.

In the centre is a map outline of East Lothian (although it notably uses the boundaries of the modern council area, rather than those of the traditional county which the flag was intended to represent) defaced with a fluttering Saint Andrew's saltire, as a homage to East Lothian's status as the birthplace of the Scottish flag.

In the canton is a white Saint Andrew's saltire (one of the arms of which resembles a beam of light), to acknowledge the county being the birthplace of the national flag of Scotland.