Source : Webster's Revised Unabridged Dictionary (1913)

Overcautious \O"ver*cau"tious\, a.
   Too cautious; cautious or prudent to excess. --
   {O"ver*cau"tious*ly}, adv. -- {O"ver*cau"tiou*ness}, n.

Source : WordNet®

overcautious
     adj : unnecessarily cautious; "sometimes it doesn't pay to be
           overcautious in business"