Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions at root s = 7 TeV, undertaken with the CMS experiment at the LHC. The b' quarks are assumed to decay exclusively to tW. The b'(b') over bar -> tW(-)(t) over barW(+) process can be identified by its distinctive signatures of three leptons or two leptons of same charge, and at least one b-quark jet. Using a data sample corresponding to an integrated luminosity of 4.9 fb(-1), observed events are compared to the standard model background predictions, and the existence of b' quarks having masses below 611 GeV/c(2) is excluded at 95\% confidence level.