The hosts were unable to bounce back after the PSV midfielder's first half opener as Oranje cruised to a comfortable victory and maintained their 100 per cent record in qualifying
The PSV midfielder slotted home at the half-hour mark after a superb pass from Wesley Sneijder, while De Jong scored from close range well into stoppage time.
The away side started the match with attacking intent and could have opened the scoring within the first minute after sloppy defending from Finland. Nevertheless, Dirk Kuyt hesitated too long and Lukas Hradecky rushed off his line to save the Liverpool man's weak shot from the edge of the area.
Netherlands then seemed to break the deadlock after 14 minutes of play when John Heitinga tapped home a rebound after Hradecky failed to hold on to a free kick from Sneijder. Nevertheless, the centre-back was judged to have been in an offside position and the goal was disallowed.
Oranje got the lead they deserved at the half-hour mark when Strootman scored his first goal for the national side. Sneijder set up the PSV youngster with a superb pass over the top of the Finland defence and the midfielder volleyed home from inside the box.
Perparim Hetemaj was Finland's biggest attacking threat and the midfielder tried his luck from 20 yards out, but his shot wasn't dangerous enough to trouble Maarten Stekelenburg between the sticks.
The World Cup finalists started the second half like the first and another intelligent pass from Sneijder set up Robin van Persie. The Arsenal forward showed superb control before firing in a right footed shot, but Hradecky pushed the ball clear with a good reflex. Again Van Persie should have added his name to the score sheet shortly after following a cross from Kuyt, but his header ended in the waiting arms of the Finland shot stopper.
Finland then came close to levelling the scoring around the hour mark with their biggest chance of the match. Hetemaj found Kasper Hamalainen with a superb long ball and the attacker lifted the ball over Stekelenburg, only to see Erik Pieters clear the ball off the goal-line.
The home side were reduced to 10 men in the 61st minute when the referee showed Hetemaj his second yellow card of the evening after an alleged dive in midfield.
The visitors continued to dominate after Hetemaj's dismissal, but Klaas-Jan Huntelaar, Van Persie and Eljero Elia all failed to beat Hradecky. Sneijder tried his luck from long range as well on two occasions, but the Inter playmaker didn't have much luck.
Substitute Luuk de Jong put the match to bed in the closing seconds of the game after Sneijder found Elia with a good long pass. The new Juventus ace laid the ball off for the Twente forward, who calmly slotted home.
Finland have accumulated nine points from eight games following Tuesday's game and are no longer in the race to qualify for Euro 2012. They host Sweden on October 7 in their penultimate qualifier.
Netherlands maintained their perfect score in Helsinki and sit atop the table in Group E with 24 points. They will qualify for next year's tournament if Sweden spill points against San Marino later on Tuesday. The Dutch face Moldova next on October 7.