Depends. If you are American a bachelors is enough but a masters can help. If you are a foreigner who wants to work in America then a Masters helps (1 year of school in the US) and gives you two slots at the lottery. Machine learning and data science jobs that are relevant in select companies usually require a PhD in math/stats/cs/engineering especially as you go up the food chain and corporate hierarchy. CS is a little more forgiving if your are adept at developing complex software systems. This is what I've observed at a few public companies that are relevant in machine learning / data science.

Grad school can also help accelerate your career especially if you can program.