The Swedish pair completed the 9.5km race in a time of 20:29.99, 1.40 seconds clear of Switzerland, with Germany taking bronze nearly six seconds down.
Dahlqvist was a late call-up for the even after sprint classical gold medallist Linn Svahn was ruled out through injury, but she had no issue keeping Sweden in front on her first circuit after Sundling had maintained a narrow lead in on the first lap.
Sundling was then pressured by Astrid Slind of Norway on lap three, but the two-time silver medallist at Milan-Cortina maintained her composure to hand her teammate a 2.3 second advantage at the third exchange.
Dahlqvist continued to gradually grow the lead, which was 4.1 seconds at the next changeover, with Finland moving into silver medal position ahead of Canada and the United States, but there were still plenty of teams in with a chance of a medal.
31-year-old Sundling then put in her fastest leg, 3:20.1, to give Dahlqvist the seemingly easy task of cruising home to win, but with the scrap for minor medals behind her, she did not let up, putting in a time of 3:17.1 to finish clear of the fast-finishing Nadine Faehndrich of Switzerland.
There was a tight finish for bronze, with Germany edging Norway by 0.14 seconds, with the United States in fifth place.
Sweden's medal tally across the games now stands at six golds, five silvers and two bronzes, with women's cross-country accounting for four golds, four silvers one bronze.