You can start as early as 4 months, I did with my daughter around that age from time to time. I think it's better because of you don't sometimes it's hard to take the bottle away. My daughter is 10 months now and she only gets sippy cups throughout the day and bottle at night

Get the soft ones to start off with they work great it might take him a min but he will like it

@lillady,

How did you start doing it. My son is going to be 6 months in a week or so and he gets upset

6 months