An undergraduate program in occupational therapy can last between 3-4 years. Further, a master's degree will take a minimum of 2 years. That makes the duration at school about 5-6 years.Thereafter, a minimum of six months of work experience is required for you to qualify for the certification exam.As such, becoming an occupational therapist can take anywhere from 7-8 years.n undergraduate program in occupational therapy can last between 3-4 years. Further, a master's degree will take a minimum of 2 years. That makes the duration at school about 5-6 years.