The Monster star adopted baby Jackson at the age of four months in March (12), just days before she had to embark on a world tour to promote her new movies Snow White and the Huntsman and sci-fi thriller Prometheus.
Theron insists she is lucky to have her 59-year-old mum by her side to lend a hand and she credits the tot with bringing mother and daughter even closer.
The actress tells America's People magazine, "She has taken to the role of grandmother like a fish to water. I have moments where I look at her and go, 'Were you this nice to me?' It heightens your relationship, which is really bizarre because I didn't think I could get any closer to my mum. I would not be able to do this without her.
"Right now, like any working mum, I've been just trying to figure out how to juggle everything. But I know what my priorities are. This is everything that I've dreamed of and about for a really long time."