We test the hypothesis that efficient internal capital markets mitigate the negative announcement returns surrounding seasoned equity offerings (SEOs). Our predictions are based on the argument that efficiency reduces uncertainty regarding the value of assets-in-place. Having established the inverse association between our efficiency measures and uncertainty, we show that the efficiency measures are positively associated with SEO announcement returns, particularly among firms with multiple segment codes. The positive relation suggests that efficiency mitigates uncertainty regarding the value of assets-in-place, and this is the channel through which more favorable announcement returns are produced in response to the SEOs of high efficiency firms.