The Toffees took an eighth-minute lead through Kevin Mirallas, who side-footed into the bottom corner from 20 yards after Hull failed several times to clear a corner.
Substitute Yannick Sagbo, a replacement for Danny Graham - who was taken to hospital for a scan on his injured knee - powerfully converted Sone Aluko's cross for his first Premier League goal on 30 minutes as Hull got themselves back on level terms.
However, 10 seconds after coming off the bench, Pienaar turned in a 57th-minute cross from Mirallas to secure Roberto Martinez's side, still unbeaten at home throughout 2013, the three points.
Below, Sports Mole analyses whether the result was reflective of the action on Merseyside.
On target: 6
On target: 1
Was the result fair?
They needed Pienaar to come off the bench to make the vital contribution, but Everton were deserving winners. Following an even first half, after which Hull entered the break with the parity that their performance warranted, the Toffees were the better side and could have increased their winning margin had they been more clinical late on. Despite conceding twice, Hull defended well for the majority, but simply did not create enough from open play to be worthy of any points today.
It was a battling team performance from the Toffees, who, on a rain-soaked Goodison Park surface, could not control their passing game as they would have liked. Their most instrumental attacking figures so far this season, Romelu Lukaku and Ross Barkley, were marked out of the game for the most parts and did not create as many clear-cut openings as they would have liked in the first 70 minutes. After Pienaar's goal, though, they limited Hull to the bare bones and looked the only team likely to add to the scores.
Steve Bruce's side's only shot on target was Sagbo's goal, but Abdoulaye Faye did present them with an aerial threat from corners. Had he, or his teammates, made the most of his headers and knockdowns, then Hull may have come away with a point, but set pieces were there only consistent method of attack. At the other end, Faye and Curtis Davies dealt with Lukaku as well as I have seen any defensive pair do so.
Sports Mole's man of the match:
The Tigers centre-back was given a warning of Lukaku's power early on, but quickly learned how to quell the threat of the big Belgian and kept him quiet for the majority of the afternoon. He also made a couple of pivotal interceptions inside his own box and helped provide Hull with an aerial threat from set pieces.
They did not prove to be costly misses in the end, but how Arouna Kone did not make it a slightly more comfortable final few minutes for the hosts, I'm not quite sure. Twice the Ivorian striker missed fantastic opportunities to net an Everton third, with the first of his efforts hitting the post when, from eight yards out, it seemingly appeared easier to score.
Neil Swarbrick was sensible in his decision-making throughout the afternoon, as there were several forceful challenges that received minimal punishment. Perhaps he should have taken action against Sagbo for his reckless tackle on Phil Jagielka in the latter stages. Swarbrick will also go down as the man who blotched the otherwise perfect copybook of Leighton Baines by booking the Everton full-back for simulation in stoppage time.
Everton: A trip to Aston Villa next Saturday, before a real test of their top-four credentials the weekend after with the visit of Tottenham Hotspur.
Hull: Consecutive trips to White Hart Lane, as they face Spurs in the Premier League and then the Capital One Cup in the space of three days.