Objective(s):  The cholinergic system plays an important role in learning and memory. This study investigated the effects of curcumin (turmeric extract) and the cholinergic system and their interaction on memory retention of passive avoidance learning in adult male Wistar rats. Materials and Methods: At first, an injection cannula was implanted in right ventricles of the animals. One week after the surgery, the animals were trained with a shuttle box set up. Post-training, injections were performed in all experiments. Administration of curcumin increased memory retention. Also administrations of nicotine and pilocarpine, the cholinergic receptor agonists, increased memory retention, while it is decreased by succinylcholine and scopolamine, the cholinergic receptor antagonists. Then co-administration of curcumin and cholinergic drugs were performed. Intraperitoneal and intracerebroventricular injections were applied for the curcumin and cholinergic drugs, respectively. Results: Co-administration of curcumin (45 mg/kg) with a low dose of nicotine (0.1 µg/rat) or pilocarpine (0.5 µg/rat) increased memory retention significantly. Effects of succinylcholine (0.01, 0.1 and 0.5 µg/rat) or scopolamine (0.1, 1 and 5 µg/rat) were attenuated by curcumin markedly (45 mg/kg). Conclusion: The results suggest that curcumin has a close interaction with cholinergic system in memory retention process.