Yes! An employer and employee can have both a health reimbursement arrangement (HRA) and a health flexible spending account (FSA) at the same time. However, the same expense cannot be reimbursed from both accounts.
Special ordering rules (i.e. "coordination rules") can be implemented to determine whether the HRA or FSA should be used first.
Unless otherwise specified in the plan documents, the HRA must be used first (prior to the FSA).