Iheanacho scored a brace for his side Leicester City as they overcame minnows Peterborough United 5 - 1 in a round of 32 fixture to achieve the feat.
Kelechi's brace in the competition puts him at nine goals more than any Nigerian has scored in the FA Cup.
The 21-year-old goal tally has surpassed Nigerian great Kanu Nwankwo and Jay Jay Okocha, who Kelechi said he will like to emulate.
Nigeria's Top Scorer's in the FA Cup.
1. Kelechi Iheanacho
9 goals in 8 FA Cup matches
Teams scored for - Manchester City and Leicester City.
2. Yakubu Aiyegbeni
8 goals in 20 FA Cup matches
Teams scored for - Portsmouth, Middlesbrough, Reading.
3. Nwankwo Kanu
6 goals in 24 FA Cup matches
Teams scored for - Arsenal, Portsmouth, West Bromwich Albion.
4. Victor Moses
6 goals in 29 FA Cup matches
Teams scored for - Stoke City, Chelsea, West Ham, Liverpool.
5. Danny Shittu
4 goals in 12 FA Cup matches
Teams scored for - Watford, Millwall FC.
6. Victor Anichebe
4 goals in 21 FA Cup matches
Teams scored for - Everton, West Bromwich Albion.
7. Victor Obinna
3 goals in 3 FA Cup matches
Teams scored for - West Ham.
8. Kayode Odejayi
3 goals in 26 FA Cup matches
Teams scored for - Barnsley FC, Colchester United, Tranmere Rovers.
9.. John Obi Mikel
3 goals in 32 FA Cup matches
Teams scored for Chelsea.
The young Iheanacho will hope to continue his goal scoring exploits with Leicester City in the FA Cup round of 16.