The Canaries struck early to stun the Fratton Park crowd as Marcelino Nunez whipped in a free-kick from the right which found Darling in a central position and the unmarked defender headed the ball into the net to give his side the lead after just six minutes.
Moments later Portsmouth nearly levelled as Josh Murphy turned before crossing the ball to the back post where Regan Poole was sprinting in but his well-struck effort was impressively saved by Vladan Kovacevic.
Norwich then doubled their lead after 14 minutes with another set-piece routine that left Portsmouth’s backline scrambling.
Darling loaded up a long throw which was flicked on by Jose Cordoba to the back post where a couple of Norwich players were running in and ultimately it was Sargent who got there first, nodding the ball home as Nicolas Schmid rushed across his goal but was unable to get there in time.
Facing an uphill struggle after the break, Pompey lost attacking midfielder Lang – who has started this season on the right wing – when he seemed to clutch his hamstring after going into a strong challenge on the edge of the box.
Lang missed several weeks of last season after tearing his hamstring in February – although he did end up returning for moments of the Blues’ final matches.
Despite his latest injury, Portsmouth played better in the second half, but the real drama did not come until the final 15 minutes of normal time.
They were handed a way back into the match as Bianchini sprinted onto a loose ball in the area and was fouled by Norwich defender Kellen Fisher. Up stepped Bishop to take the spot-kick but his effort was saved in the right corner by Kovacevic.
There was, though, to be no clean sheet for Norwich as new signing Segecic picked up the ball and beat Kovacevic from outside the box to give the home fans late hope.
Portsmouth appealed for a penalty in the fifth minute of added time as Connor Ogilvie went down in the box but the referee awarded a free-kick to Norwich for simulation.
The home side continued to push in the final moments and John Swift hit the underside of the crossbar with a volleyed effort from the edge of the box, but Norwich held on for all three points.