We have investigated the effects of substituting In for Mn on the antiferromagnetic phase transition in Y MnO3 using magnetic, dielectric, and specific heat measurements. We prepared a set of isostructural phase pure hexagonal Y Mn1-xInxO3 samples having x = 0 to x = 0.9, which exhibit a systematic decrease of the antiferromagnetic ordering temperature with increasing In content. The multiferroic phase, which develops below TN, appears to be completely suppressed for x ≥ 0.5 in the temperature range investigated, which can be attributed solely to the dilution of magnetic interactions as the crystal structure remains hexagonal. Similarly to previous reports, we find an enhancement of the magnetocapacitive coupling on dilution with non-magnetic ions. © 2010 Elsevier Ltd. All rights reserved.