The G protein subunits Gqα and G11α (Gq/11α) couple receptors to phospholipase C, leading to increased intracellular calcium. In this study we investigated the consequences of Gq/11α deficiency in the dorsomedial hypothalamus (DMH), a critical site for the control of energy homeostasis. Mice with DMH-specific deletion of Gq/11α (DMHGq/11KO) were generated by stereotaxic injection of AAV-Cre-GFP into the DMH of Gqαflox/flox:G11α-/- mice. Compared to control mice that received DMH injection of AAV-GFP, DMHGq/11KO mice developed obesity associated with reduced energy expenditure without significant changes in food intake or physical activity. DMHGq/11KO mice showed no defects in the ability of the melanocortin agonist melanotan II to acutely stimulate energy expenditure or to inhibit food intake. At room temperature (22oC) DMHGq/11KO mice showed reduced sympathetic nervous system activity in brown adipose tissue (BAT) and heart, accompanied with decreased basal BAT Ucp1 gene expression and lower heart rates. These mice were cold intolerant when acutely exposed to cold (6oC for 5 hours) and had decreased cold-stimulated BAT Ucp1 gene expression. DMHGq/11KO mice also failed to adapt to gradually declining ambient temperatures and to develop adipocyte browning in inguinal white adipose tissue although their BAT Ucp1 was proportionally stimulated. Consistent with impaired cold-induced thermogenesis, the onset of obesity in DMHGq/11KO mice was significantly delayed when housed under thermoneutral conditions (30ºC). Thus, our results show that Gqα and G11α in the DMH are required for the control of energy homeostasis by stimulating energy expenditure and thermoregulation.