Both players made major contributions in Leicester City's cup run, culminating in the triumphant scenes at Wembley after they edged Chelsea 1-0 to claim a first ever FA Cup title for the club and the duo themselves.
Kanu, who won the FA Cup with Arsenal (twice) and Portsmouth as well as Olympic gold with Nigeria, was thrilled for them.
"It is wonderful to see them as FA Cup champions," the former Nigeria captain told ESPN. "They needed to go for it and they did. Congratulations to them, they did really well.
"This will now give them the belief that they can go and do more. When you win one, you want to win another and another one. At least you know that you have won the FA Cup. The next thing now is to look for more trophies and it gives them more confidence and more encouragement and the belief that they can do anything and win against anybody."
Winning the FA Cup comes as something of a personal triumph for Iheanacho, who has endured really trying times since joining the Foxes from Manchester City in the summer of 2017.
The forward struggled to establish himself in the side and things got so bad that Nigeria coach Gernot Rohr not only questioned his attitude to work, but left him out of the squad for the 2019 Africa Cup of Nations in Egypt.
Iheanacho was forced to work his way back into both the Leicester side and his national team. Despite an impressive preseason, it was not until September that he got his first taste of Premier League action, a five-minute cameo in Leicester's 5-2 victory against his former employers Manchester City.
Iheanacho has emerged from those dark days to become a starting fixture for Leicester and Kanu said the way he handled adversity is the mark of a great player.
"He has gone through some really bad times and I know what a lot of people have said about him when he was in those low periods," he said. "But we know it is football. When you are not doing well, people talk anyhow and say what they want but when you start doing well, the same people come back.
"For me, I always know he is a good footballer. I always talk with him, encourage him, send him messages when he is doing well and when he is not doing well and telling him to keep his head up.The only thing was for him to work hard, Talent with hard work works. If you believe only on the talent, it will disappoint you so you have to marry the two together.
"It is something great that he is back now. Not only for himself but for the country. We need all our players to be in top form. Right now he is. If you mention the top strikers in the world now, Kelechi's name will be there because he is scoring and that is what you need from strikers. What happened to him is a very big lesson, and the way he responded is what makes a great player. He didn't talk too much, he just worked hard and see where he is now."
Kanu, who played in four FA Cup finals, appreciates the importance of the trophy after losing a final with Arsenal in 2001 before winning back-to-back titles in 2002 and 2003 and then scoring the winner in Portsmouth's 2008 triumph.
"It is very very important," he added. "If you ask anybody in England they will tell you that the FA Cup means a lot. It is the oldest cup. Whoever touches that cup has done great. Not everyone has reached the final let alone win it.
"Every player who plays in England has a dream of playing the FA Cup Final at Wembley and winning it. So it is a massive one for them just getting there and I am very proud of them that they not only got to the final, but also won it."
Chelsea dominated large aspects of the game, with 13 shots on goal to Leicester's six, 65% possession and 85% pass accuracy to Leicester's 74%, but Kanu said lifting the trophy is what matters in the end.
"When you play a cup final, what matters in the end is not whether you played well or not, but who wins at the end," he said. "You don't have to play well to win the cup. It is better to play badly and win. The most important thing is that you want to win the cup, that you have to give extra of whatever you have been giving before because you really want to win.
"That means that if they were giving 100 percent before, they now have to give 150%. Give so much more that after the game, you can't even walk because you know you have given your best and left everything out there on the pitch."