The effect of dispersity on the stabilization performance of poly(butyl methacrylate) (P(BMA)) w-unsaturated macromonomer used as a reactive dispersant in nonaqueous acrylic dispersion (NAD) polymerization is investigated for the first time. Macromonomer with low dispersity (1.3) is synthesized in a one-pot process by the addition of bis(difluoroboryldiphenylglyoximato)cobalt(II) (CoPheBF) as a catalytic chain transfer (CCT) agent to P(BMA) chains mediated by atom transfer radical polymerization (ATRP); addition of the CoPheBF at a BMA monomer conversion of similar to 80% leads to good control of chain length and dispersity while achieving a high fraction of terminal double bond (TDB) functionality. The lower dispersity P(BMA) macromonomer provides better stabilization to NAD systems per dispersant chain compared to material of the same number-average molecular weight (similar to 6000 Da) and TDB functionalization (similar to 70-75%) but higher dispersity (1.8), as characterized by the smaller average particle sizes and the higher weight fractions of incorporated dispersant.