It can take anywhere from four weeks to three months to become a certified nursing assistant. Depending on the specific program and student schedule, the programs are divided into classroom hours and clinical practice based on state criteria. However, if you want to get into the field as soon as possible, there are accelerated programs that take only a few weeks to complete. If your schedule is more hectic, you may prefer a longer part-time option. Make sure to look into several different programs to find one that meets your requirements.