Studies in mice with targeted deletions of tachykinin genes suggest that tachykinins and their receptors influence emotional behaviors such as aggression, depression and anxiety. Here, we investigated whether TAC1- and TAC4-encoded peptides (substance P and hemokinin-1, respectively) and the neurokinin-1 receptor (NK-1R) are involved in the modulation of sexual behaviors. Male mice deficient for the NK-1R (TACR1 −/−) exhibited decreased exploration of female urine in contrast to C57BL/6 control mice and mice deficient for NK-1R ligands such as TAC1 −/−, TAC4 −/− and the newly generated TAC1 −/− /TAC4 −/− mice. In comparison to C57BL/6 mice, mounting frequency and duration were decreased in male TACR1 −/− mice, while mounting latency was increased. Decreased preference for sexual pheromones was also seen in female TACR1 −/− mice. Furthermore, administration of the NK-1R-antagonist L-703,606 decreased investigation of female urine by male C57BL/6 mice, suggesting an involvement of NK-1R in urine sniffing behavior. Our results provide evidence for the NK-1R in facilitating sexual approach behavior, as male TACR1 −/− mice exhibited blunted approach behavior toward females following the initial interaction compared with C57BL/6 mice. NK-1R signaling may therefore play an important role in pheromone-induced sexual behavior.