The Scottish Rugby Union has confirmed the Australian will step up from his role as senior assistant coach to take caretaker charge following Andy Robinson's resignation as head coach last month.
The coaching team remains as it was for the autumn Tests, but the SRU will soon appoint an interim forwards coach and a global search for Robinson's permanent successor is continuing.
Robinson used to oversee the pack and the SRU could now turn to another ex-England flanker, with Neil Back already an employee as forwards coach at Edinburgh.
Scotland's Six Nations campaign begins on February 2 against England at Twickenham and Johnson will receive an indication of the form of many of his players when Glasgow Warriors host Edinburgh tomorrow night before the return fixture in the RaboDirect PRO12 eight days later.
"It's an honour to take charge of the national team for our imminent campaign," Johnson said.
"I will be doing everything I can to bring the best out of our players as we all seek to achieve winning performances."
It will be hoped Johnson can emulate, at least in part, Stuart Lancaster, who was so impressive as England interim head coach during last year's Six Nations that he was appointed on a permanent basis following four wins from five matches.
England at least had a wealth of playing resources at Lancaster's disposal, even if he inherited a mess from the World Cup fiasco which prompted Martin Johnson to quit.
Scotland showed promise under Robinson, beating Australia (twice), South Africa and Argentina, but the abject showing in the 21-15 loss to Tonga left him frustrated, angry and out of a job and onlookers wondering if the players who admitted they had let him down could be consistent forces in Test rugby.
Robinson stood down after three-and-a-half years in charge on November 25, the morning after the Tonga defeat which left Scotland 12th in the International Rugby Board world rankings following 10 losses in 13 Tests.
Scotland had won just two of 15 Six Nations matches under Robinson, who appointed Johnson as senior assistant coach in a reshuffle which followed the 2012 Six Nations whitewash.
Former United States Eagles and Ospreys head coach Johnson was once in caretaker control of Wales, where his time was marred by rumours of player power forcing the exit of previous boss Mike Ruddock.
The 50-year-old helped to oversee Scotland's successful summer tour to Australia, Fiji and Samoa before November losses to New Zealand, South Africa and Tonga resulted in Robinson's resignation.
SRU chief executive Mark Dodson said: "Scott has a wealth of experience of international rugby, which was instrumental in his appointment earlier this year as our senior assistant coach.
"He has coached with Australia, Wales and the USA and knows what it is to prepare teams to win on the international battleground.
"Scott knows our players and coaches well and is determined to hit the ground running with a successful RBS 6 Nations Championship."
Johnson's support team will be comprised of assistant coach Matt Taylor (defence) and specialist coaches Duncan Hodge (kicking and catching) and Massimo Cuttitta (scrummaging), with a forwards coach soon to be appointed on an interim basis.