This study investigates the cellular processes underlying cell shape determination in *Haloferax volcanii*, a model archaeon that forms rods and disks under different growth conditions. Using a combination of proteomics, genetics, and live-cell imaging, the researchers identified mutants that form only rods or disks. By comparing the proteomes of these mutants with wild-type cells across growth phases, they distinguished between protein abundance changes specific to cell shape and those related to growth phases. The results identified a diverse set of proteins, including transporters, transducers, signaling components, and transcriptional regulators, as crucial for cell shape determination. Specifically, they found that rod-determining factor A (RdfA) and disk-determining factor A (DdfA) are essential for rod and disk formation, respectively. Additionally, they identified a structural protein, volactin, an actin homolog involved in disk-shape morphogenesis. Live-cell imaging revealed that volactin assembles into dynamic filaments and exhibits a different dynamic behavior compared to bacterial MreB. The study provides insights into archaeal cell shape determination and suggests potential implications for understanding the evolution of cell morphology regulation across domains.This study investigates the cellular processes underlying cell shape determination in *Haloferax volcanii*, a model archaeon that forms rods and disks under different growth conditions. Using a combination of proteomics, genetics, and live-cell imaging, the researchers identified mutants that form only rods or disks. By comparing the proteomes of these mutants with wild-type cells across growth phases, they distinguished between protein abundance changes specific to cell shape and those related to growth phases. The results identified a diverse set of proteins, including transporters, transducers, signaling components, and transcriptional regulators, as crucial for cell shape determination. Specifically, they found that rod-determining factor A (RdfA) and disk-determining factor A (DdfA) are essential for rod and disk formation, respectively. Additionally, they identified a structural protein, volactin, an actin homolog involved in disk-shape morphogenesis. Live-cell imaging revealed that volactin assembles into dynamic filaments and exhibits a different dynamic behavior compared to bacterial MreB. The study provides insights into archaeal cell shape determination and suggests potential implications for understanding the evolution of cell morphology regulation across domains.