Star striker Sunil Chhetri put defending champions India ahead when he converted from the spot in the 71st minute in controversial circumstances.
The other three goals were scored by Clifford Miranda (79th), Jeje Lalpekhula (80th) and Sushil Singh (injury time) after Afghanistan were reduced to 10 men following the marching orders by the referee on Afghanistan goalkeeper Hameedullah Yousefzari.
The whole drama started as soon as the referee Sukhbir Singh from Singapore awarded a penalty after Jeje was brought down by Afghanistan central defender Faisal Safa.
The decision was questionable but Afghanistan goalkeeper Hameedullah Yousefzari took things in his own hand by pushing the referee.
The result was a red card which forced the visitors to play with 10 men for the last 20 minutes at Jawaharlal Nehru stadium, which witnessed a turnout of about 5000 spectators, the highest in the tournament.
Afghanistan, who were playing in their maiden final, lost their bearings once their goalkeeper was sent off and India capitalised the advantage to the full.
Afghan coach, Yousef Kargar, was in a quandary as he had to sacrifice a regular player to accommodate his reserve goalkeeper. He brought in reserve goalkeeper Bashir Ahmad at the expense of winger Ghulam Hoddein.
The Indians, meanwhile, regrouped after a mediocre display in the first half. Chhetri, whose first spot kick was disallowed because of intrusion by Nirmal Chhetri, ensured that he was on target after he was asked by retake the penalty.