Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV) persists endemically in dromedary camels across Western Africa and the Middle East. There has been a precipitous decline in human cases post-SARS-CoV-2 pandemic potentially linked to cross-reactive immune mechanisms. To investigate this phenomenon, we conducted integrated serological profiling of abattoir and herders in MERS-CoV endemic areas, RT-PCR-confirmed MERS-recovered patients, diverse SARS-CoV-2-exposed groups (varied infection/vaccination types), and pre-pandemic controls using 1) screening a panel of MERS antigens with limited homology to SARS-CoV-2; 2) Comprehensive IgG subclass and Fcγ receptor binding assays to MERS Spike domains and Nucleocapsid; and 3) functional cellular assessments of FcγR-mediated antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Our antigen results revealed distinct MERS-CoV-specific humoral signatures towards MERS structural proteins N and M, in endemic camel workers and MERS-recovered patients. Additionally, we observed significantly enhanced FcγR-binding functionality and conventional IgG antibody responses against MERS Full Spike and N in MERS-recovered patients. Parallel assessments uncovered functionally relevant cross-reactive humoral responses in SARS-CoV-2-exposed cohorts, particularly targeting the partially conserved Spike Subunit 2, with corresponding amplification of ADCC effector functions across SARS-CoV-2-vaccination groups (BNT162b2 and CoronaVac). These findings showed SARS-CoV-2 immunity induces cross-reactive Fc-functional responses through conserved epitopes, and FcγR-mediated effector mechanisms may modulate population susceptibility to MERS-CoV. The convergence of Fc-effector functions across beta-coronavirus exposures provides a framework for understanding reduced MERS vulnerability in SARS-CoV-2-exposed populations and informs development of pan-betacoronavirus countermeasures targeting conserved functional domains.