With a cup final still to come, winning the league keeps the Capital side on course for a double next month and means they will be in Europe next season.
Watsonians were crowned champions after beating nearest rivals Clydesdale Western 3-0 at Titwood last night in their 19th league victory on the spin. They have won every match since losing on the opening day of the season.
They will round off their league campaign against Edinburgh University on Sunday and can still do the double when the face students again in the Scottish Cup final May 15.
Smith said: “It was very much a team effort, we have a big squad and everyone has played their part at one time or another, both on and off the pitch. Everybody has worked hard for this success. But Clydesdale and Edinburgh University pushed us hand during the campaign.”
Mairi Drummond, Ellie Stott and Sarah Jamieson were the Watsonians scorers last night, the Edinburgh side defending well and clinical on the counter-attack.
Smith added: “I would say that 3-0 possibly flattered us, we had to soak up a lot of pressure during the game but we defended well. But we took our chances and that was the difference.”
Scottish international striker Emily Dark admitted: "We were nervous as it was such a big game and we have gone so long unbeaten in the league and cup.
"Clydesdale also beat us in the first game of the season, 1-0 at Peffermill, and it was a game we should have won. They had patches, but we felt in control.
"It was a great game, very enjoyable, and we now move on to the final game of the league season against Edinburgh University on Sunday and the cup final in May. We're also in Europe next season.”
Edinburgh University can clinch the runners-up spot and a European place with three points at home to Hillhead on Saturday before they face the champions on Sunday.
Relegation in the lower half of the table is all but sorted – Erskine Stewarts Melville are automatically relegated while Grove Menzieshill appear to locked in to the play-off spot.