Competing in the event for the first time, the 25-year-old finished in a time of one hour, 58 minutes 56 seconds to hold off Canada's Kirsten Sweetland and compatriot Vicky Holland.
Stimpson, who was overlooked for the London 2012 Olympics, ended five seconds clear of Sweetland with Holland 10 seconds further back.
In a field missing world champion Non Stanford and three-time World Championships gold medallist Helen Jenkins, Stimpson proved too strong.
There was positive news for two home favourites at the Tollcross Swimming Centre, as Scottish pair Michael Jamieson and Hannah Miley both qualified for finals.
Jamieson - an Olympic silver medallist in 2012 - will contest the men's 200 metre breaststroke after finishing second in his heat, while Miley beat her own Commonwealth record to make the 400m individual medley final.
They will contest two of six finals later on Thursday, while the first medals will also be handed out in the weightlifting.
Nigeria's Rasaq Tanimowo lifted a total of 225 kilograms in Group B of the men's 56kg to set the early standard ahead of the first two finals later in the day.
Australia and England - both medallists in Delhi four years ago - picked up early wins over Malaysia and Wales respectively in the women's hockey.
The home crowd saw all six Scottish entrants make their respective judo finals with sisters Kimberley and Louise Renicks among the successful domestic contingent.
Defending Commonwealth champion Natalie Melmore got her title bid under way with a 21-7 win over Carmela Spiteri while South Africa - dominant in Delhi four years ago - picked up a win in the women's fours.
Commonwealth squash gold medallist Nick Matthew is safely into the next round after an opening-day win over Xavier Koenig of Mauritius with Singapore and India making the early running in the table tennis at the Scotstoun Stadium.
Malawi and Australia were early netball winners thanks to victories over Northern Ireland and Wales.