The true answer depends on how mature your child is. The major thing you will have to deal with is that they may be excited at first to get the hamster and take care of it but after a while they may become bored of it and not want to take care of the pet anymore. With a nine-year old having the hamster might bring juy for a couple weeks but soon it will be a drag for the kid to feed and water and change its bedding, and then you will be telling them to do those things all the time. They may not take care of it and it could starve, and die. So if you have a mature enough child that would be responsible enough to continue taking care of a pet then I would say yes. The only reason I would say no is because if they are not mature they will eventually not take care of it and it could starve or be a challange to have that 9 year old do a job they might not want too.