Patterned conductive structures have attracted significant attention as important components of printed and flexible micro/nanodevices. However, the fabrication of conductive micro/nanostructures with controlled and well-organized morphologies is a key challenge in the development and application of micro/nanoelectronic devices based on low-dimensional materials. To meet the requirements of depositing conductive structures on specific substrates, electrohydrodynamic jet (E-jet) printing, developed as a simple and effective method for fabricating micro/nanopatterns of polymers, was combined with a conventional wet metal etching process for patterning conductive metals on polymer substrates. Under optimized experimental conditions, we achieved fine straight-line patterns with a line spacing of 1 μm at a nanoscale printing resolution (average line width: 68 nm) and grid patterns with variable spacings and grid line widths, down to size of 871 nm. Furthermore, fully printed graphene photodetectors were obtained through in situ direct writing, and their photoelectric response to a change in photocurrent of 0.22 μA was demonstrated. The results suggest that combining E-jet printing with chemical etching is a promising mask-free approach for producing conductive metal patterns for micro/nanoelectronic devices.