The Collaborative International Dictionary of English v.0.48:

Mistrustful \Mis*trust"ful\, a.
   Having or causing mistrust, suspicions, or forebodings.
   [1913 Webster]

         Their light blown out in some mistrustful wood. --Shak.
   [1913 Webster] -- Mis*trust"ful*ly, adv. --
   Mis*trust"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mistrustful
    adj 1: openly distrustful and unwilling to confide [syn:
           leery, mistrustful, suspicious, untrusting,
           wary]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "mistrustful":
   Pyrrhonic, agnostic, cagey, chary, distrustful, doubtful, doubting,
   dubious, from Missouri, in doubt, leery, mistrusting, questioning,
   scrupulous, shy, skeptical, suspecting, suspicious, uncertain,
   untrusting, wary