<i>Background:</i> The uncoupling proteins (UCPs) and β-adrenoceptors (ADRBs) are important for energy balance and may be involved in the pathogenesis of insulin resistance. Obesity is strongly hunted by insulin resistance and susceptibility genes for the two conditions could be separate or common. Variations within the <i>UCPs </i>and <i>ADRBs </i>genes may give important clues to their involvement in disease. <i>Methods:</i> A total of four single nucleotide polymorphisms (SNPs) in the genes <i>UCP1, UCP2, UCP3, and ADRB1</i> were examined for association with obesity and insulin sensitivity (HOMA_IR) in obese (n = 292) and healthy non-obese (n = 481) females. <i>Results:</i> None of the SNPs was associated with obesity status or body mass index. However, <i>ADRB1 </i>(rs1801253) was nominally associated with serum insulin (nominal p = 0.034) and HOMA_IR (nominal p = 0.022). <i>UCP3</i> (rs1800006) was in post-hoc analysis nominally associated with serum insulin and HOMA_IR (nominal p = 0.013 and 0.048, respectively).<i> UCP1 </i>and <i>UCP2</i> showed no association with insulin sensitivity. <i>Conclusion:</i> Polymorphisms in <i>ADRB1</i> and <i>UCP3</i> may contribute to insulin resistance rather than obesity among Swedish women.