The Notting Hill star hit headlines in November (11) when he revealed he had a one-month old daughter following a "fleeting affair" with former model Tinglan Hong.
Grant has remained silent about his child and the relationship, but he's revealed all about how fatherhood has affected him in an interview with Britain's Guardian Weekend magazine.
Revealing that his little girl is called Tabitha, he says, "I did feel a little lumpy (emotional) when I first met my daughter, yeah. Lots of people said, 'Never let anyone know, but the baby period is not that exciting.' But I am excited, actually.
"I thought, well, I'll bluff through - but very little bluffing has been required. I like my daughter very much. Fantastic. Has she changed my life? I'm not sure. Not yet. Not massively, no. But I'm absolutely thrilled to have had her, I really am. And I feel a better person."
Grant is keen to instil a sense of discipline in his daughter at a young age, adding, "There's a lot of over-parenting, to my eye, anyway. I do think discipline's important.
"I'm very glad that I had quite a strict mother who was big on discipline, because you really cannot get anything done in life if there's too much, 'Oh, well, if you don't feel like it, don't do it, just express yourself,' I'm not really very big on that."
And the 51 year old is adamant he will not be leaving his fortune to Tabitha, as he wants her to learn the value of money the hard way.
He adds, "My other worry is about - and as I say, there are few things in life I believe in 100 per cent - but another one is not giving your children money. I see nothing but f**k-ups among my trust-fund friends. It's like 99 per cent f**k-ups. So I would not want to do that to my children, no."
Tabitha, who lives mainly with her mother, also has a Chinese name, and Grant is planning to learn the language to help his daughter become bilingual.
He explains, "I haven't given it the attention it needs yet. I do know some disgusting Chinese words. They're not entirely appropriate for baby rearing."