Along with his victory in the Edinburgh Central seat on May 6, it marks a dramatic return after a period outside of elected office for the former deputy leader of the SNP
Mr Robertson is one of the new faces in Nicola Sturgeon’s Cabinet, announced on Wednesday.
While the 51-year-old is a political veteran, it is the first time he has been a Scottish Government minister.
The portfolio covers constitutional policy, European and wider external relations, as well as post-Brexit issues.
With the SNP committed to pushing for a second independence referendum during the current parliamentary session, Mr Robertson’s views on the constitution will shape much of the political debate in coming years.
Perhaps best known as the SNP’s Westminster leader for a decade-long period, he lost his seat in Moray to Douglas Ross in 2017.
Mr Robertson first joined the SNP when he was 15, campaigning in its youth and student wings before unsuccessfully standing for election in Midlothian’s Holyrood seat in 1999.
He has worked as a journalist, including for the BBC World Service as a foreign correspondent.
Mr Robertson’s electoral breakthrough came in 2001 when he won in Moray, representing the constituency in the House of Commons for the next 16 years.
He would go on to lead the SNP group in the Commons from 2007, becoming a familiar face at Prime Minister’s Questions.
While MP for Moray, he was influential in the SNP’s campaigns for the 2007 and 2011 Scottish Parliament elections, and the 2015 general election – acting as the party’s campaign director.
Following his defeat in 2017 he set up the pro-independence think-tank Progress Scotland, which commissioned opinion polling around independence.
Last year he announced he would run for election in Edinburgh Central, the seat held by former Scottish Conservative Ruth Davidson who stepped down from Holyrood.
However, his path to the seat was not entirely clear as he faced a selection contest against former SNP minister Marco Biagi to be the party’s candidate.
MP Joanna Cherry also intended to run for Holyrood in Edinburgh Central, but later pulled out, saying party rules would have “hobbled” her candidacy.
Mr Robertson secured a majority of 4,732 in the election.
During his victory speech, he said: “In this most European of capital cities, people have resoundingly rejected the party of Brexit and Boris Johnson.
“The public has rejected all of the parties that want to block an independence referendum.
“This result is an emphatic and an unparalleled victory for the SNP in Edinburgh Central.
“We have just won the seat of the former leader of the Scottish Conservatives and recorded the best ever SNP result.”
Asked about the fact he has never held a ministerial role before, Ms Sturgeon said: “Angus is hugely experienced as a politician.
“He led the SNP Westminster group in the wake of that 2015 election result that saw a massive group elected, so he’s very experienced.”