Ade Gardner went over for Saints after 46 seconds and Jamie Lyon added a second try just before half-time.
Chris Thorman kept the Giants in touch with two first-half goals and a third after the restart before a try from Brad Drew reduced the deficit to two.
Maurie Fa'asavalu hit back with a try for Saints and a late Stephen Wild try was not enough for the hosts.
St Helens coach Daniel Anderson
"Once again our defence kept us in the game. We're not attacking very well at the moment.
"We seem to be playing teams who are really up for us.
"Huddersfield were very solid but I didn't feel anxious about the result. I felt we deserved to win the game."
Huddersfield: Reilly, Aspinwall, Evans, De Vere, Donlan, Thorman, Paul, Crabtree, Drew, Nero, Snitch, Wild, Jones, Jackson, March, Smith, McDonald, Raleigh, Gardner, Torrens.
St Helens: P. Anderson, V. Anderson, Bennett, Cayless, Cunningham, Fa'asavalu, Gardner, Gilmour, Hardman, Hooper, Long, Lyon, Meli, Moore, Pryce, Roby, Sculthorpe, Talau, Wellens, Wilkin.