The event is an informal opportunity for fans to remember Niehaus this week. Plans for a formal memorial celebration are pending, and the club will release details as soon as a final decision is made on that in conjunction with his family.
Fans may enter Saturday's open house through the Home Plate entrance and then will be invited to sign a remembrance book for the Niehaus family, view memorabilia of his Hall of Fame career and share memories.
There will be no formal program at the event, so fans can arrive any time in the three-hour window that the park will be open.
An online tribute page for Niehaus is also available at www.mariners.com/dave, where fans can post messages and see highlights of his career.