A retainer includes a retention module surrounding a heat sink and two clip members for cooperating with the retention module to retain the heat sink. Each clip member includes a strap resting on the heat sink and a pair of legs located at opposite ends of the strap and engagable with the retention module. The legs are pivotably attached to opposite ends of the strap. Friction between the legs and the strap is capable of holding the legs at any positions between released positions at which the legs are free from the retention module and engaged positions at which the legs are engaged with the retention module.