This article analyses how the corporate valuation of Latin American firms is affected by the presence of a blockholder institutional investor. The study uses a data set of 562 firms from six Latin American countries for the 1997–2011 period. We found that the presence of an institutional investor has a positive effect of 8% on firm value, which increases to 21% for the cases where there is blockholder coalition with an institutional investor. After dividing the sample by investor type, we found that independent institutional ownership implies a positive premium on firms' Tobin's Q, while the presence of a grey investor has a negative effect on firm valuation.