The 31-year-old's goal, just after he came on as a second-half substitute, extended Everton's unbeaten Premier League home record in 2013 to 13 games and brought to an end Hull's four-match unbeaten run.
Pienaar, who had missed four league matches with a hamstring problem, admitted it was a bit of a dream after a troubled start to his campaign.
"I think it was a lucky touch," he told Sky Sports.
"But at the end of the day it went in and I'm happy we got all three points and for me after the last seven weeks it was something I worked hard for and it finally paid off.
"I wanted to get a few minutes to get used to the tempo of the game, but to get a goal and the win itself is something that I'm really happy about."