In this work, omniphobic surfaces are developed by combining chemical etching and surface modification of aluminum. In the first step, hierarchical micro/nanostructuring is carried out by chemical etching. Thereafter, a perfluoropolyether is grafted onto the corrugated aluminum substrate, decreasing its surface free energy and turning the system omniphobic. The morphology and chemical composition of the developed surfaces are characterized. We observed a low affinity toward liquids, regardless of their chemical nature and surface tension. The surface shows superhydrophobic properties with a water contact angle of 160 degrees and simultaneously strong oleophobic properties with a hexadecane contact angle of 141 degrees. Furthermore, these omniphobic surfaces significantly delay the freezing time of water droplets to 5100 s, which is about 20-fold of the freezing time on pristine aluminum (260 s), and they even inhibit ice growth by repelling the incoming droplets prior to ice nucleation.