Potassium bromide (KBr), an old antiepileptic agent, is illegally used in pharmaceutical or food industries to improve the product appearance. KBr has been proven to influence several pathways which are important in memory formation. Therefore, the present study aimed to evaluate the effect of KBr on spatial working memory using object recognition task (ORT). Rats received a single dose of KBr (50, 100 or 150 mg/kg), per oral, in acute treatment. KBr long term effects were also studied in animals receiving 50 mg/kg/day of KBr for 28 consecutive days. At the end of treatments, animals underwent two trials of ORT, five min each. In the first trial (T1), animals encountered with two identical objects for exploration. After 1 h, the animals were exposed to a familiar and an unfamiliar object (T2). The exploration times for discrimination (D) and recognition (R) as well as the frequency of exploration for any objects were determined. Acute administration of 150 mg/kg of KBr significantly decreased the discrimination and recognition indices (RI and DI) (P < 0.01) compared to the control. However, lower doses failed to influence the animals’ performance in the test. In addition, long term administration of KBr remarkably diminished the DI and RI and the frequency of exploration (P < 0.05). The results of this study indicate that acute doses of KBr as high as 150 mg/kg are required to hamper memory function in ORT. However, cognitive impairment occured with lower doses of KBr when the duration of treatment is extended.