Mujeeb returned figures of 9.5-0-43-4, including three wickets in four balls of his last over, as the Windies were skittled out for 204 in 46.5 overs after electing to bat first.
Shahzad stroked his second successive half-century while hitting a 93-ball 84 with 11 fours and two sixes to steer his side home with 9.2 overs to spare.
These stellar performances came after 19-year-old Rashid Khan, the world's number-one ranked ODI bowler, had become the fastest bowler to 100 ODI wickets. He achieved the feat in his 44th ODI when he dismissed Shai Hope to beat Australia's Mitchell Starc's record in 52 ODIs.
This is Afghanistan's first major ICC title after they had finished second to Ireland in the 50-over ICC World Cricket League Championship in 2013. The side, which was playing in the ICC World Cricket League Division 5 until 2008, has won the four-day first-class ICC Intercontinental Cup twice (2009-10, 2015-17) and ICC World Twenty20 Qualifier 2010.
The title is also special for Afghanistan as they won five straight matches after being on the verge of an early flight home following three consecutive losses.
In the past three decades, only Pakistan and Australia are the two countries who have returned from the dead to win titles. Pakistan won five straight matches to win the ICC Cricket World Cup 1992, while Australia won six matches on the trot to win the ICC Cricket World Cup 1999.
As for the two-time former world champions, the 50-over title drought continues despite twice winning the ICC World Twenty20 in 2012 and 2016. Their last 50-over title was in 2004 when they won the ICC Champions Trophy in England. They reached the final of the ICC Champions Trophy 2006, where they lost to Australia.
"This trophy is for the people of Afghanistan," a delighted Afghanistan captain Asghar Stanikzai said, adding, "This is nothing but a miracle that we have won this tournament. This would not have been possible without the prayers, support and well-wishes of all our fans. This title is for them."
Accrediting the whole team for the victory, an emotional Stanikzai further remarked, "I think it is a victory of self-belief and self-confidence. This victory will give us the required boost to work extremely hard over the next 14 months and like the other nine sides, will arrive in England and Wales firmly believing we can win the World Cup."
Windies captain Jason Holder said, "Well done to Afghanistan, especially the way they played after the group stages. Having said that, I'm proud of my boys. We came here to achieve a target, and various boys put their hands up. We had a quick turnaround between games, but I'm proud of them for sticking in. Obviously disappointed not to win this final but we had some great performances throughout. I want to thank my team for their support."
Meanwhile, Zimbabwe's Sikandar Raza was declared Player of the Tournament.
Earlier, the Windies innings never reached the take-off point as they continued to lose wickets at regular intervals. No.7 batsman Rovman Powell finished as the top scorer with a 75-ball 44, while Shimron Hetmyer (38), Evin Lewis (27), Ashley Nurse (26 not out) and Shai Hope (23) were the other batsmen to cross the 20-run mark.
Mujeeb was once again the destroyer in chief of the Windies' batting. Opening the bowling, he immediately put the Windies on the back foot when he accounted for Chris Gayle, before picking up three wickets in his 10th over to finish with four for 43.
Gulbadin Nain snapped up two for 28, while Dawlat Zadran, Sharafuddin Ashraf and Rashid Khan picked up a wicket apiece, but most importantly didn't allow the Windies batsmen to change gears.
In turn, Shahzad played some exciting strokes to all parts of the park as he single-handedly put his side on course for a comfortable victory when he scored 84 off 93 balls with 11 fours and two sixes. He put on 58 runs for the first wicket with Gulbadin and added 90 runs for the second wicket with Rahmat Shah.
After Shahzad's departure, Gayle also accounted for Rahmat Shah (51, 78b, 4x4) but it was too late as Afghanistan achieved the victory target for the loss of three wickets in 40.4 overs. Seasoned all-rounder Mohammad Nabi finished with a flourish, clobbering Gayle for three consecutive sixes to the cheer of his enthusiastic team-mates. (ANI)