Resistive switching memory devices based on three-dimensionally confined Ag quantum dots (QDs) embedded in polyimide (PI) layers were fabricated by using spin-coating and thermal evaporation. The Ag QDs embedded in PI layer were distributed uniformly with sizes of approximately 4-6 nm and with surface density of approximately 1.25 x 10(11) cm(-2). The electrical properties of the Ag/PI (10 nm)/Ag QDs/PI (10 nm)/Ag devices were investigated at room temperature. Current-voltage (I-V) measurements on the devices showed a counterclockwise electrical hysteresis behavior with reliable and reproducible resistive switching to the existence of the Ag QDs. The memory device transformed from its original high-resistance state to low-resistance state under positive bias, and regained its original high-resistance state under negative bias. The maximum ON/OFF ratio of the current bistability was 1 x 10(4). The device also revealed excellent endurance ability at ambient conditions. The possible operating mechanisms concerning the interaction between Ag QDs and PI matrix for the resistance-transform phenomenon were analyzed on the basis of the I-V results.