Isothermal crystallization rates of semicrystalline poly(methoxypoly(ethylene glycol) methacrylate) brushes on gold-coated substrates were measured by polarized optical microscopy. Growth rates for crystal radii, which were essentially constant for each film, initially increased with film thickness and then leveled off for film thicknesses >300 nm. Avrami-Evans theory suggests that the spherulites exhibit one-dimensional growth with heterogeneous nucleation. Compared with physisorbed analogs, polymer brushes crystallized slower due to the restriction of chain mobility. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1955-1959, 2010