ABSTRACTThe continuous evolution of SARS‐CoV‐2 through accumulating mutations, combined with the persistent risk of zoonotic sarbecovirus transmission events, highlights the critical demand for broadly protective vaccines. Building on our previous findings that a heterodimeric receptor‐binding domain (RBD) design substantially improves cross‐reactive immunogenicity in vaccine candidates, we propose this strategy as a foundation for developing pan‐sarbecovirus vaccines with cross‐neutralizing capacity against diverse and emerging variants. In this study, we developed a sarbecovirus immunogen, utilizing a heterodimeric strategy incorporating the RBDs from both SARS‐CoV and SARS‐CoV‐2. Pseudovirus neutralization assays revealed that mice immunized with the SARS‐CoV‐2 prototype (PT)‐SARS‐CoV heterodimer (PT‐SARS) developed 39.9‐ to 305.6‐fold higher neutralizing antibody (NAb) titers against SARS‐CoV‐2 sub‐variants compared to the SARS‐CoV RBD homodimer (SARS‐SARS). Furthermore, PT‐SARS elicited 17.6‐ and 31.2‐fold enhanced neutralization against WIV1 and SARS‐CoV, respectively, relative to the SARS‐CoV‐2 PT homodimer (PT‐PT). To address evolving Omicron sub‐variants, we further updated BA.1‐SARS and BA.2‐SARS immunogens. Notably, BA.2‐SARS exhibited a 6.2‐fold increase in neutralizing potency against BA.2.86 compared to PT‐SARS. Crucially, the heterodimeric immunogen induced balanced and broadly reactive NAbs against multiple sarbecoviruses, including RaTG13, Pangolin GD, SARS‐CoV, and SARS‐CoV‐2 variants/sub‐variants, demonstrating its potential as a sarbecovirus immunogen candidate.