This study explores whether speaker emotion influences communicative effectiveness. Two hundred participants rated their current emotional state and gave a description of a route on a simple map. The quality of the linguistic content of the descriptions was assessed using Latent Semantic Analysis. Six hundred participants provided route drawings based on the map descriptions. Median route deviation served as a measure of communicative effectiveness. Eighty additional participants rated invariant parts of the descriptions for perceived speaker happiness. Path analysis revealed that while speaker emotion did not affect the linguistic content of the descriptions, it had an effect on communicative effectiveness both through the effects of vocal cues directly as well as mediated by perceived happiness of speech. Specifically, higher first formants were associated with higher reported and perceived happiness as well as higher communicative effectiveness. Jitter, on the other hand, was negatively related to the perception of happiness and positively related to communicative effectiveness. These findings suggest that mood-related modulation of phonation and articulation can influence the effectiveness of communication in addition to message content.