Widnes (6) 12 Tries: Hanbury 2 Goals: Hanbury 2 St Helens (16) 20 Tries: Greenwood, McCarthy-Scarsbrook, Makinson Goals: Walsh 4 St Helens sent early pacesetters Widnes to a second successive Super League defeat and a first home loss of 2016.
The Vikings began the Easter programme top of the table, but followed Friday's defeat at Warrington with a second loss to one of their local rivals.
Tries by Joe Greenwood, Louie McCarthy-Scarsbrook and Tommy Makinson gave Saints a 16-6 lead at half-time.
Rhys Hanbury scored all 12 points for Widnes, including two tries, but Saints survived a late flurry to earn victory.
Widnes stay two points behind leaders Warrington, who saw their 100% start ended by Hull FC on Monday.
St Helens, the 2014 champions, are two points further behind after bouncing back positively from their derby defeat by Wigan on Good Friday.
Greenwood's fourth try in four games gave them a perfect start and, although Widnes drew level shortly afterwards through full-back Hanbury, they struggled to create meaningful attacking opportunities until the final 10 minutes.
There were also not helped by the loss of forward Hep Cahill to an injury which prevented him featuring after half-time.
Having added the extras to two of Saints' tries and kicking two further penalties, Saints scrum-half Luke Walsh made a try-saving tackle to deny Corey Thompson a score with 13 minutes to play.
His intervention would prove crucial as Hanbury's second try sparked Widnes and raised hopes of a comeback, but the visitors held on for their fifth win of the campaign.
Widnes head coach Denis Betts: "I just said to the players that it's a double-edged sword. We defended well, especially the second half, but we let ourselves down with the ball.
"We put so much into our defence and we had a bad day with the ball.
"Some of our decision making wasn't there. Things didn't stick. Some of the calls went against us but we are own worst enemy on some of those decisions with players putting hands in where we shouldn't."
St Helens head coach Keiron Cunningham: "We played for the full 80 minutes, we are a good side and we played some great stuff.
"It's tough over the Easter period - I know as I've done it for years, so it's important that we got the win.
"Widnes defended well, we had to work hard and we came here knowing what we needed to do and we got the job done."
Referee: Richard Silverwood. Super League, officially the First Utility Super League for sponsorship reasons, is the top-level professional rugby league club competition in Europe. The league has twelve teams: eleven from England and one from France. The current champions are Leeds Rhinos.
Super League began in 1996, replacing the RFL Championship and switching from a winter to a summer season. Each team plays 23 games between February and July: 11 home games, 11 away games and a Magic Weekend game at a neutral venue. At the end of the season, the top eight teams enter a Super 8 stage, playing each other once more. The top four then enter the play-off series leading to the Grand Final (formerly Championship Final) which determines the champions.
The average Super League match attendance was 8,365 in 2014.[1] The Super League champions play the National Rugby League (NRL) champions from Australasia in the World Club Challenge.
Contents History 1996–2001: Establishment 2002–2008: Promotion and relegation 2009–2014: Licensing 2015-Present: Super 8s Clubs Current clubs Former Super League Clubs Non-English Teams All Time Super League table Point deductions Venues Derbies Hull Derby Good Friday Derby Cheshire Derby Calder derby Coaches Head Coaches with multiple Super League titles Players Appearances Tries Points Structure World Club Series Regular Super League season Magic Weekend Challenge Cup Super 8s Play-offs Grand Final Awards League Leader's Shield Super League Trophy Steve Prescott Man of Steel Award Super League Dream Team Champions Winners The Double The Treble All Four Cups Sponsorship Competition rules Club trained players Salary cap Squad announcement system Criticism Big Four Dominance Licensing M62 Corridor Match officials Academies Reserve League Dual registration Under 19s