Tries from fellow Magners League players Tommy Bowe and Martyn Williams, together with another from Ugo Monye, looked set to see the Lions home, before the boot of Willem de Waal and a Joe Pietersen try threatened to bring an unexpected end to the tourists' 100-per-cent record.
Having only been on the field for 13 minutes after Leinster full back Rob Kearney had suffered a dead leg, Hook defied a strong wind to kick the Lions to victory from 45-metres.
The Magners League again played a big part for the Lions with eight of the league's players starting at Newlands and two more making an appearance from the replacements bench.
As well as try-scoring performances from Bowe and Williams and Hook's late heroics, there were strong displays from Magners League team-mates Andy Powell and Kearney with both pushing their Test claims ahead of next weekend's first international against world champions South Africa.
Ian McGeechan's men bounced back from the disappointment of losing Magners League trio Stephen Ferris, Leigh Halfpenny and Ryan Jones to injury earlier in the week to keep up the momentum ahead of that highly-anticipated showdown in Durban a week today.
The majority of the opening half in Cape Town was dominated by the boot, with two Stephen Jones penalties being superseded by a penalty and a drop goal from de Waal and a further drop from full back Pietersen.
The result was a three-point advantage to the home side after 27 minutes before two superb tries turned the game in the Lions' favour.
Bowe was heavily involved in both efforts, somehow escaping the clutches of Pietersen to cross for the first on 28 minutes before slicing through the Western Province defence to set up wing partner Monye for the second seven minutes later.
Powell confidently claimed a high ball on his own 10-metre line wide on the left before charging through the opposition and taking play back towards centre field. Rather than going to ground, as he had done predominantly during the win over the Cheetahs, the Wales No8 kept the ball alive with a deft offload to countryman Williams.
The Lions openside performed his traditional link role perfectly, taking the ball from Powell, turning his back into the onrushing defence and feeding scrum-half Harry Ellis to keep the visitors well and truly on the front foot.
Ellis moved possession wide, Keith Earls provided a decoy run and Kearney supplied the scoring pass.
Bowe still had plenty to do but, just as he had done in the opening two matches on tour, the Ospreys star made light work of what was in front of him. Three Western Province defenders were unable to bring Bowe to ground as he span out of one tackle and ran straight through two more before forcing the ball down five metres in from the right-hand touchline.
Jones was off-target with the attempted extras but he made no mistake from an identical position on the opposite side of the pitch following Monye's 35th-minute score.
This time, Bowe turned creator, taking Jones' pass behind the first line of attackers on halfway and gliding between the Western Province midfield before producing a brilliant offload that set Monye free.
Bowe's floated five-metre pass allowed Monye to continue at full speed and the Quins wing showed his growing maturity with a diving finish that made the most of the wet ground and ensured the covering defence would be unable to drag him into touch.
Jones' well-taken conversion gave the Lions a nine-point advantage and, with the way in which they finished the games against the Sharks and the Golden Lions, it looked as though they may run away with proceedings now that they had finally established some breathing space.
It wasn't to be, however, as Western Province showed the same kind of character displayed by the Sharks for 40 minutes on Wednesday for a full 80 this afternoon.
Penalties either side of half-time from de Waal immediately cut the deficit to just three points and, although a Williams try again hinted at what might have been for the Lions, Western Province refused to give up the fight.
Whereas the tries from Bowe and Monye had come from quick ball and expert finishing out wide, showing what the Lions are capable of when space opens up in front of them, Williams' effort was a far more conservative, yet equally impressive score.
Forward power allowed the Lions to recycle passion repeatedly inside the Western Province 22, with the squad collective preventing anyone player from breaking off without the support of his team-mates.
Patience was the key as the Lions continued to drive forward and Williams was the man to spot the gap when it finally opened up. The veteran flanker marked his return from a shoulder injury with a timely reminder of his abilities and it was he who broke off the back of a maul as it descended into another ruck four metres shy of the opposition line.
Williams spotted scrum-half Dewaldt Duvenage defending the narrow blindside and simply barged his way through his more lightweight opponent to send the Lions eight points clear with 25 minutes left to play.
Jones failed with the attempted conversion from wide on the left but it again appeared as though the Lions may have received the boost they needed to move on and control the remainder of the match.
The Lions failed to build on that advantage, though, as a fourth penalty from de Waal brought the home side back to within a single score.
That score was then supplied by Pietersen, following a strong burst from second row Anton Van Zyl and suddenly the Lions were in real danger of falling to a shock defeat.
Momentum was back with the South African side and the Newlands crowd sensed a first victory over the Lions since 1938. The Lions could easily have folded and therefore suffered a major setback prior to Saturday's clash with the Boks but instead they stuck to their task and finished the stronger of the two sides.
Just as they had done against both the Cheetahs and the Royal XV earlier in the tour, the Lions stayed focused under pressure and were rewarded for that composure when they were given a brace of penalties in the closing stages.
Hook missed with the first of those attempts just three minutes after coming on following Pietersen's try but he made no mistake with the second to secure another valuable victory for the Lions.
The Magners League is again expected to have a heavy contingent when the Lions play their final warm-up fixture against the Southern Kings on Tuesday evening.
Despite the withdrawals of Ferris, Halfpenny and Jones during the tour itself, and the enforced absence of Tomas O'Leary, Tom Shanklin, Alan Quinlan and Jerry Flannery prior to departure, a total of 25 Magners League players are still involved with the Lions.
Each and every player will be desperate to play in the three-match series against Peter de Viliers' Boks, with Tuesday's clash the final opportunity to secure a Test place.
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