Q fever is a worldwide zoonotic disease caused by an obligate intracellular gram-negative bacterium Coxiella burnetii. Q-VAX, the current human Q fever vaccine, is an inactivated whole-cell preparation that induces reactogenic responses in previously sensitized individuals. Here we developed a safe and particulate subunit vaccine candidate that is ambient-temperature stable and can be cost-effectively manufactured. We bioengineered an endotoxin-free mutant of Escherichia coli to efficiently self-assemble biopolymer particles (BPs) that are densely coated with T-cell epitopes (COX-BP) or two immunodominant antigens (BP-XY) derived from C. burnetii. Safety and immunogenicity were confirmed in mice and guinea pig models. BP-XY elicited specific and strong humoral immune responses in guinea pigs with significant IgG titers that were at least 1000 times higher than antibodies induced by Q-VAX. We also demonstrate that vaccinating guinea pigs with BP-XY prior to C.burnetii challenge is capable of eliciting protective immunity that significantly reduced fever responses and bacterial burden in liver tissues compared to the mock vaccinated guinea pigs. These data suggested that BP-XY induces functional immune responses to prevent infection by C. burnetii and illustrates the potential of BPs as an effective antigen carrier for Q fever vaccine development.