Andrew Keith was knighted and created Lord Dingwall in 1584 by James VI of Scotland. He was keeper of the castle of Dingwall. He became a confidante of James Stewart, Earl of Arran, who appreciated his efforts as a diplomat in Sweden and England.
He went to Denmark to negotiate the king's marriage to Anne of Denmark. He was paid £1,666-13s-4d Scots for the expense of fitting up two ships for his voyage. In July 1589 Dingwall and his fellow ambassadors George Young, and John Skene came to Boyne Castle to bring James VI news from Denmark of the progress of the marriage negotiations and preparations of ships, jewels, and a silver coach for Anne of Denmark. However, in Denmark the presence of Andrew Keith in the embassy, as a man in Swedish service, had caused offence. John Colville, who was at Aberdeen with the royal party, heard that the ambassadors had not seen Anne of Denmark in person. James VI decided to send Dingwall back to Denmark. Thomas Fowler, also at Aberdeen, had heard a rumour that the embassy had caused some confusion in Denmark, the marriage being considered as settled, and costly preparations in hand, a circumstance that could bring disgrace to the lady and the Danish council "in most parts of Europe". Dingwall returned from Denmark on September 1589 and reported that he had seen Anna of Denmark and her fleet, commanded by the Danish admirals Peder Munk and Henrik Gyldenstierne, at the northern tip of Denmark, at Skagen. The English ambassador William Ashby heard that the queen would arrive in five days in the best of conditions, and the wind was favourable. Dingwall was picked to travel to Norway to fetch the queen, then included in the king's party in Norway and Denmark. In January they travelled overland through a part of Sweden, Anne of Denmark and James VI in sledges sent by her mother Sophie of Mecklenburg-Güstrow. John III king of Sweden had sent special instructions that Andrew Keith and Axel Gyldenstierne should on no account be allowed in the fortress of Älvsborg at the mouth of the riverGöta. There was discussion whether the queen's dowry money should be brought home untouched to Scotland, or whether the Earl Marischal, Dingwall and William Keith of Delny should be recompensed.
Sweden again
Andrew Keith resigned his lands to Sir William Keith of Delny and returned to Sweden. He came to Scotland in January 1598 on a mission from the king of Poland, and James VI gave him a gold chain worth 300 crowns. He intended to recruit men for service in Sweden but according to Roger Aston he had no money to enlist them, and people were discouraged because earlier recruits had been "cruelly slain." He was exiled from Sweden after the coup in 1598 and died in Paris in 1606. Andrew Keith married Elizabeth Grip in 1574. She wrote to the Earl Marischal in August 1584 thanking him for the help he had given them. They had a house in Stockhom, and ran a network of intelligence agents in Sweden.