Leslie just snatched third by a blink, finishing .07s ahead of Turkey's Beytullah Eroglu.
Wellington's Mary Fisher followed Pascoe's gold with a silver medal in her 400m freestyle final.
Fisher, who has a genetic eye condition, was beaten by Paralympic gold medallist Daniela Schulte of Germany, who touched in 5min 25.24s. Fisher, who has already won two gold medals earlier in the championships, was second in 5:28.06, with Olga Iakibiuk third 28s behind Fisher.