Gender roles and expectations for women have been shown to account for why women tend to negotiate ineffectively in business settings. Drawing from the psychological literature on multiple identities, this paper examines how individual differences in perceived compatibility between gender and professional identities-captured by the construct Gender-Professional Identity Integration (G-PII)-shape businesswomen's negotiation behaviors. Two studies examined how G-PII interacts with identity cues and cue valence to influence negotiation outcomes. We found that those who perceived their gender and professional identities as compatible (high G-PII) exhibited an "assimilation" effect-they negotiate more effectively when their professional identity was primed by professional identity cues and when prototypical female traits were positively linked to negotiation success, and negotiated less effectively when their gender identity was primed by gender identity cues and when prototypical female traits were negatively linked to negotiation success. However, businesswomen who perceived their gender and professional identities as incompatible (low G-PII) exhibited the opposite "contrast" effect. These findings suggest that the way women negotiate is influenced in part by individual differences in perceptions of compatibility between multiple identities.