Canada won the toss and put the South Africans into bat and the latter amassed 213 for four in their 20 overs.
The Canadians managed 156 for eight in reply, never threatening the South African score despite some handy knocks.
Captain Aiden Markram top-scored for South Africa with 59 from 32 balls, with several others chipping in. David Miller (39 not out from 23 balls) and Tristan Stubbs (34 not out from 19) put on an unbeaten 75 for the fifth wicket in 37 deliveries.
The left-arm wrist-spin of Ansh Patel caused South Africa some alarm as he recorded figures of 3-31 in his four overs.
Ngidi tore through the Canada top order, reducing them to 26 for three, and it was an uphill slog for them from there despite an excellent 64 from 49 balls from Navneet Dhaliwal.
"You have to find a way to take wickets and take some risks," Ngidi said. "Sometimes you go for boundaries but bowling risky balls sometimes end up in the wickets column."
Canada were an unknown quantity for South Africa, who had to adapt quickly, Ngidi admits.
"That's one of the things we struggled with, gameplans for guys you haven't seen much of. It was trial and error, we tried something and had a chat. Worked it out as we go. But pretty straightforward with the new ball.
"We knew our attack brings pace but for me variations catch people out. I tried to do what I do best, change it up and keep guys guessing."
Marco Jansen (2-30), Kagiso Rabada (1-40) and Corbin Bosh (1-27) were also among the wickets.
South Africa are next in action against Afghanistan in a crucial day clash at the same venue on Wednesday, which will be a trial by spin for the Proteas.
They also have New Zealand and United Arab Emirates in their pool.
"It was important (to win), we've seen at the start, anyone can beat anyone. You don't take anyone lightly. All three areas we were solid tonight," South Africa captain Markram said.
"We bowled really well, there was a bit on offer and then the dew came in. We asked questions, tried to take wickets and got it right more often than not.
"(Afghanistan were) semi-finalists in the last edition, it's a day game as well, so we have to be on it."
