Andersson finished 1.3 seconds faster than the Norwegian in a time of 30:19.8, 12 seconds faster than her compatriot, Frida Karlsson, who claimed bronze.
The gold and silver podium places matched those of the 20km skiathlon on Sunday, when Andersson reclaimed the title she won two years ago by less than a tenth of a second.
The conditions on Tuesday were much more difficult, with athletes having to contend with heavy snow which makes the classic technique more tough.
Andersson was the 34th competitor out onto the course in Trondheim, with Johaug following a minute afterwards.
The 27-year-old Swede's early split times were down on the Norwegian, who was fastest at the 2km and 3.2km marks.
But Andersson pushed hard over the second half of the event, and took what turned out to be the fastest time at the 9.2km split.
The Swede crossed the line but had to wait for Johaug to finish to see if she had done enough. For the second time in three days, the 36-year-old came up short, taking her second silver medal.
Andersson took bronze in this event at the 2023 World Championships, but thought a gold medal was beyond her;
"A gold on 10 kilometres classical is not really something I even dared to think about in my wildest fantasy," she exclaimed.
Sweden have now won five medals at the championships so far, all coming in women's cross-country events. Jonna Sundling took gold in the sprint freestyle and bronze in the skiathlon.