The 50-year-old Aberdonian had started the final round two shots behind Australian Peter Fowler in the £250,000 event on the East Lothian coast.
But, in the toughest conditions of the three days, he closed with a 71 for a two-under-par 211 total and a two-shot triumph over Fowler (75) and Englishman Peter Baker (70).
The win came in just Lawrie’s third regular event on the Staysure Tour, having joined the senior ranks at the start of this year.
It was his fourth big success on Scottish soil as a professional after The Open (1999), Dunhill Links Championship (2001) and Johnnie Walker Championship (2012).
He won the Dimension Data Pro-Am in South Africa in 2017, but this welcome win was his first since returning from a spell on the sidelines due to back and foot problems.
It was the second year running that the Scottish Senior Open title had fallen to a home player after Gary Orr triumphed at the same venue 12 months ago.