Olefin polymerization in the presence of heterogeneous supported catalysts is improved by incorporating into the supported catalyst a unifunctional hydrophobic tether comprising a hydrophobic portion containing no basic nitrogen and a univalent reactive group. The unifunctional hydrophobic tether reduces fouling and sheeting in gas phase polymerization processes and improves polymer morphology and bulk density in slurry polymerization processes, while substantially maintaining or enhancing catalyst polymerization activity.