Imamoğlu was projected to win 28 of Istanbul's 39 districts with 54.0% of the overall vote in the mayoral elections rerun, unofficial results showed on Sunday, Trend reports citing Daily Sabah.
In the March 31 local elections, Imamoğlu won 16 of the districts, a dramatic difference from his dominant performance Sunday.
Imamoğlu's opponent, People's Alliance candidate Justice and Development Party's (AK Party) Binali Yıldırım, lost 12 districts compared to the March elections.
The vote difference between the two candidates was 777,581, significantly higher than 13,729 announced after March 31 elections.
Imamoğlu's biggest win was in Beşiktaş district, where he received 83% of the vote, followed by Kadıköy with 81% and Bakırköy with 79%. Yıldırım's biggest lead was in Sultanbeyli with 65% of the vote, followed by Esenler and Arnavutköy with 61% and 60% respectively.
Imamoğlu received the biggest boost in Adalar district, where he increased his votes by 10 percentage points compared to the last election. Çatalca and Silivri districts came second with a change of 8 percentage points, followed by Avcılar, Bakırköy and Şişli with 7 percentage points.
The CHP candidate managed to flip Bahçelievler, Bayrampaşa, Beykoz, Beyoğlu, Çekmeköy, Eyüpsultan, Fatih, Sancaktepe, Şile, Tuzla, Üsküdar and Zeytinburnu districts compared to the March elections.
Soon after the results began coming in, Yıldırım conceded defeat and congratulated Imamoğlu on his apparent victory.
Yıldırım and Imamoğlu are vying to run the metropolitan municipality of Turkey's most populous city after a previous vote on March 31 was annulled by the country's top election council last month.
On March 31, Imamoğlu received 48.8% of the vote, whereas Yıldırım got 48.55%, according to official figures from the Supreme Election Council (YSK).