A flexible filter retainer and a holding frame assembly having a flexible retainer are provided. In one embodiment, the flexible filter retainer for the holding frame comprises a flat body extending from a first end to a second end. The body comprises a bowed shaped retaining portion disposed at the first end and comprises a first strip and a top face. The body also comprises a fixed portion disposed at the second end and comprises a second strip. The first and second strips are linearly aligned and laterally offset from the top face. In another embodiment, a filter holding frame assembly comprises a holding frame and flexible filter retainers coupled to the holding frame. Each retainer comprises a flat body extending from a first end to a second end. The body comprises a retaining portion disposed at the first end and a fixed portion disposed at the second end.