Iceland headed to Cardiff looking to secure a League A play-off place at the expense of their unbeaten Welsh hosts, with Craig Bellamy’s side still carrying aspirations of topping Group B4 ahead of Turkey.
Thoughts of winning the group were indeed put on ice when a dominant start from the visitors saw them take a deserved early lead.
A patient Icelandic attack culminated with Orri Oskarsson forcing an acrobatic save from Danny Ward before Andri Gudjohnsen spun and slotted in the rebound to silence the Welsh crowd.
After a period of building pressure, Wales found themselves back on level terms shortly after the half-hour mark thanks to Cullen, who met Brennan Johnson’s curling delivery with a deft header from six yards to mark his first international goal.
With both sides vying to assert themselves in a closely contested opening half, Cullen doubled his tally deep into added time as Wales pressed ahead.
Harry Wilson’s forced turnover sprung Wales into attack, and when Dan James’ low effort was parried into the path of Cullen, he was well-placed to follow up and fire home.
In a similar vein to the first half, Iceland looked dangerous early in the second period, with the visitors repeatedly prising Wales open.
Jon Dagur Thorsteinsson twice went close to levelling, curling an effort inches wide before having a shot bundled clear off the goalline.
Despite Iceland's attempts to restore parity, another incisive Welsh breakaway saw them extend their lead with Cullen releasing Johnson to slot the ball underneath Hakon Valdimarsson.
Iceland’s discipline began to wane as their hopes faded, with Antonio Nobre issuing a spate of bookings to further add to their frustrations.
With victory now firmly within their sights, Cullen battled to win possession high up the field, launching another stinging Welsh counter as Wilson picked up possession and fired a dipping effort from over 20 yards to spark jubilant scenes and effectively wrap up the contest.
The victory leaves Wales with three wins and three draws under Bellamy’s tenure, whilst Iceland lose their fourth-straight match on Welsh soil after a promising start.
See all of the stats from this match here.
See all the results from the Nations League here.