Kevin Pringle has been in charge of the SNP’s communications and media operation for nearly three years - a period that included the independence referendum and last month’s General Election.
Mr Pringle took on the SNP role after leaving his post as chief spin doctor to Mr Salmond’s government, which he held between 2007 and 2012.
However, he will now take up a role as a partner at the Charlotte Street Partners, which describes itself as a strategic communications company and that takes on work in the public relations sector.
Mr Pringle will continue to work for the SNP for the next few weeks, but will be based at Westminster where the party now holds 56 of Scotland’s 59 MPs.
He said: “Following a remarkable and intense few years of political campaigning, I’m looking forward to a fresh challenge in the private sector. Charlotte Street Partners is an exciting young business with a high-quality team.
“They already have an impressive mix of major clients and I am keen to play my part in helping to take the business forward. My final few weeks with the SNP will be spent at Westminster, where the new-look House of Commons promises to provide a fascinating experience.”