We demonstrate an organic memory-transistor device based on a pentacene-gold nanoparticles active layer. Gold (Au) nanoparticles are immobilized on the gate dielectric (silicon dioxide) of a pentacene transistor by an amino-terminated self-assembled monolayer. Under the application of writing and erasing pulses on the gate, large threshold voltage shift (22V) and on/off drain current ratio of ∼3×104 are obtained. The hole field-effect mobility of the transistor is similar in the on and off states (less than a factor of 2). Charge retention times up to 4500s are observed. The memory effect is mainly attributed to the Au nanoparticles.