The Collaborative International Dictionary of English v.0.48:

Genealogist \Gen`e*al"o*gist\, n. [Cf. F. g['e]n['e]alogiste.]
   One who traces genealogies or the descent of persons or
   families.
   [1913 Webster]

WordNet (r) 3.0 (2006):

genealogist
    n 1: an expert in genealogy