According to some researchers romantic relationships (or pair-bonds) are the adult instantiation of attachment in childhood. This chapter reviews research on the neural correlates of early-stage, newlywed, and long-term pair-bonds highlighting how the dopamine reward system (implicated in motivation and goal-directed actions) mediates their formation, establishment, and maintenance. I also discuss activation of serotonin, vasopressin and opioid rich regions of the raphe and ventral pallidum found among newlyweds and long-term pair-bonds as reflecting the emergence of attachment in adults. Similarly, I discuss results on the association of relationship length with brain activity to further elucidate markers for pair-bond solidification. Finally, I review key sites common for pair-bonds and parent-child bonds as reflecting attachment in areas associated with reward, goal-directed actions, calm, homeostasis, and attention. Collectively, these results highlight how the brain mediates attachment processes (e.g., proximity-seeking, felt security, and responsiveness) that are critical for the solidification and maintenance of pair-bonds, and the evolutionary success of the species.