We present a search for associated Higgs boson production in the process pp¯→WH→WWW*→l±νl′±ν′+X in final states containing two like-sign isolated electrons or muons (e±e±, e±μ±, or μ±μ±). The search is based on D0 run II data samples corresponding to integrated luminosities of 360–380 pb−1. No excess is observed over the predicted standard model background. We set 95% C.L. upper limits on σ(pp¯→WH)×Br(H→WW*) between 3.2 and 2.8 pb for Higgs boson masses from 115 to 175 GeV.Received 20 July 2006DOI:https://doi.org/10.1103/PhysRevLett.97.151804©2006 American Physical Society