Lajong went ahead in the ninth minute through A Dipanda but Aizawl equalised in the 67th minute through W Lalnunfela as the two sides split points in a highly-anticipated match at the Jawaharlal Nehru Stadium.
Despite Mohun Bagan defeating Chennai City FC 2-1 in a simultaneous match in Kolkata, Aizawl ran away with the title to script a fairytale story.
Aizawl ended the league on 37 points while Mohun Bagan finished second on 36. They have won the I-League title in their second season, becoming the first club from the Northeast to bag the title.
Aizawl would not have at all played in the I-League this season as they finished eighth last year but after a few Goan sides pulled out of the country's top-flight league, they got a lifeline to stay afloat.
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Their feat is comparable to the unheralded English Premier League side Leicester which won the title in 2015-16 season after they were on the verge of relegation the previous year.
The match, the Northeast derby, was though not without controversy as Aizawl played under protest after finding out that the title-deciding game would be conducted by officials from Bengal.
Aizawl protested because Kolkata side Mohun Bagan were also in title contention and playing a simultaneous match. The Northeastern club said that they have earlier requested the AIFF to appoint neutral match officials from other states.