The 17-year-old made her debut in the World Cup last season but failed to win in her four starts, however she quickly changed that at the inaugural women's big air event.
Walker recorded an overall points tally of 156.5 points from her two best runs, with Sina Candrian (155.75) and Cheryl Maas (154.25) completing the top three.
It was Maas who started the stronger after Walker had topped qualification, the Dutch boarder recording a score of 88.50 to lead after the opening run by three points.
However, Walker was not to be denied and after her second run was not scored due to it being her lowest of the three, she put everything together on the final run.
She outscored all her rivals with 71 points to take the win, leaving her delighted to have claimed a first World Cup title.
"Most amazing night ever," she posted on Twitter. "Still can't believe I won the #worldcup here in #istanbul!
"Congrats to the legends Cheryl Maas and Sina Canadrian for laying down incredible tricks. So stoked to stand on the box with you girls!"
With only two big air events in the World Cup program the boarders will now have to wait until February in Austria to compete again.