Humphries and Ciochetti's aggregate four-run time of three minutes 48.57 seconds meant they preserved the lead they enjoyed at halfway and improved on their bronze medal at last year's event in Koenigssee, Germany.
Germany's Sandra Kiriasis and Petra Lammert had to settle for silver, by 0.33s, with Americans Elana Meyers and Katie Eberling in bronze, a second behind the winning time.
"It feels amazing. It is another goal accomplished," Humphries said.
"This means a lot to me. I feel like I'm still growing as a pilot and I try to learn from every experience. I have been working on my consistency and I'm glad it showed here."
In the men's two-man bob, Lydon Rush and Jesse Lumsden of Canada took the lead after two runs, with the USA team of Steven Holcomb and Steve Langton in second place just 0.12 seconds adrift.
Germany's Maximilian Arndt and Kevin Kuske were third, a further 0.09 seconds back.