On-loan Leicester striker Tyrese Shade's second-half goal proved the difference as Walsall extended their unbeaten League Two run to six matches thanks to a narrow 1-0 victory at Sutton.
It was the hosts who looked most likely to score, but substitute Shade came off the bench and fired home a fine free-kick to condemn Sutton to only their second home defeat since August.
Brendan Kiernan's early half-volley was well saved by Sutton's Dean Bouzanis, before George Miller sliced an effort over.
Ali Smith squandered a great chance when he flicked David Ajiboye's cross wide from close range.
The hosts caught Walsall on the counter with only the post stopping Isaac Olaofe from opening the scoring.
And Matt Gray's side went close again when captain Rob Milsom fired just over.
Sutton were left to rue those missed chances as Shade hit his 20-yard free-kick around the wall and beyond Bouzanis after 67 minutes.
Dangerous Ajiboye did well to fashion a chance on the right and fired against the crossbar with Carl Rushworth beaten.
Coby Rowe's rasping last drive flew wide as hopes of a late point slipped away.
And Saddlers stopper Rushworth recovered from a poor late clearance to keep out Enzio Boldewijn's effort.