Yes. You may participate in both a 403(b) and a 401(k) plan. However, certain restrictions may apply to the amount you can contribute. For instance, you are allowed to make a salary deferral contribution of up to $18,500 in 2018, plus an additional catch-up contribution $6,000 if the employee is 50 or older. The combined total salary deferral contribution that you make to both the 401(k) and the 403(b) plans should not exceed $18,500 or $24,500 if you qualify for the catch-up.
Note: 403(b) plans include a special provision that allows you to make salary deferral contributions of additional amounts up to $3,000 if you have at least 15 years of service with certain employers. If you meet the 15-year requirement and would like to contribute the additional amount, you should check with your employer regarding the eligibility requirements and applicable rules.
To learn more, read The Differences Between 401(k) and 403(b) Plans.
This question was answered by Denise Appleby